RV Electrical Safety: Part IV – Hot Skin

Aug 25th, 2010 | By | Category: RV Safety

The No~Shock~Zone: Part IV – Hot Skin

Understanding and Preventing RV Electrical Damage

Copyright Mike Sokol 2010 – All Rights Reserved

If you’ve read the survey we did July 2010 in www.RVtravel.com, you know that 21% of RV owners who responded have been shocked by their vehicle. Review the 21% report at http://new.noshockzone.org/15/.  What follows is #4 in a 12-part series about basic electricity for RV users and how to protect yourself and your family from shocks and possible electrocution.

This series of articles is provided as a helpful educational assist in your RV travels, and is not intended to have you circumvent an electrician. The author and the HOW-TO Sound Workshops will not be held liable or responsible for any injury resulting from reader error or misuse of the information contained in these articles. If you feel you have a dangerous electrical condition in your RV or at a campground, make sure to contact a qualified, licensed electrician.

The Big Picture

If you’ve been diligently reading this series, you should at this juncture understand the basic concepts of what voltage is, how to read it with a meter and how to check the polarity of a campsite power outlet. If not, then go back and review parts I, II and III on RV electrical safety.

But why is this concept of voltage and polarity so important? Well, one of the greatest dangers of RVing, perhaps second only to a fire (which is really terrifying) is getting shocked and possibly electrocuted when touching the skin of your RV. And while some campers may have been injured by a bare wire on an extension cord or while poking their fingers in a power panel without proper precautions, the majority of RV shocks come when you least expect them, from the skin of your RV while simply opening the door.

Hot Skin

An RV Hot-Skin condition occurs when the frame of the vehicle is no longer at the same voltage potential as the earth around it. This is usually due to an improper power plug connection at a campsite or garage AC outlet. Now to be honest, I think the majority of campgrounds have properly wired and maintained power pedestals, but certainly there are instances where a campsite has outlets with reversed polarity or without proper grounding at all. But I’ve seen enough “rewiring” jobs to know that RV owners are also to blame for improper wiring of their own extension cords and 30-amp adapters.

The scenario could go something like this: You plug your RV plug into a loose or worn campsite power outlet. Everything seems fine until you crank up your air conditioner and turn on your coffee maker. That’s when you notice the smell of burning plastic and find that the male plug on your RV extension cord has melted down due to all that current going through a loose connection. Rather than throw that expensive extension cord away, you go to your local big box store and buy a new power plug. However, when you take the wires off of the old plug there’s no diagram to show you how to connect the new plug properly. If you guess right while putting on a new plug, then all is well. If you guess wrong, then you’ve reversed the polarity of your incoming AC power. After that it just takes the right combination of circumstances such as a rainstorm to wet the ground in front of your RV, and you touching the screen door with a damp hand while standing outside. That’s when you can get shocked or even electrocuted. The severity of the shock can vary from a mild tingle to stopping your heart, depending on how wet you and the ground are and the voltage of your RV skin. But make no mistake, rather than the 30 or 40 volts of a high-resistance tingle, it’s possible to have the skin of your RV go to 120 volts with full current of the campsite pedestal with 20, 30 or even 50 amps available.


The reason we don’t notice this Hot-Skin condition until it’s too late is that an RV is basically a big metal frame sitting on rubber tires. And those tires act as electrical insulators just like the rubber surrounding the metal wire of your extension cord. That means that the skin of your RV can be electrically charged with 30, 60 or even 120 Volts with no visual indication of the problem until you complete the connection to the earth with your hand. Then because your own body provides a low resistance path to earth (remember the pipes between the water tanks in Part I of this series), current will flow through you to the ground. How much current is really the subject of another article, but if your hands and feet are wet your body becomes a 1,000-Ohm resistor connected from your hand on the doorknob to your feet on the ground. This will allow over 100 mA (milliamperes) of electrical current to flow through your heart. Tests have shown that as little as 10 mA to 20 mA of a 60-Hz current (what comes out of your electrical outlet) can cause your heart to go into fibrillation (essentially a heart attack). So you can easily get 10 times the current needed to kill yourself from a 120-volt outlet. Note that 100 milliamps of current isn’t enough to trip a standard 20- or 30-amp circuit breaker, but it’s supposed to trip a GFCI (Ground Fault Circuit Interrupt) as long as it’s been properly connected. But don’t risk your life on untested technology — check for Hot-Skin conditions before you get shocked.

Making a list, checking it twice….

 What follows are two ways to determine if the skin of your RV has been electrified. One method involves using a voltmeter just like we learned about in Part II of this series, while the second method uses a non-contact AC tester like you see electricians use to check for live outlets. Both methods are described below. But be aware that even if you tested your RV when you made camp and found it safe from a Hot Skin condition, that could change at any time if something happens to the campsite power after you’ve plugged in. If you feel even the slightest tingle from your RV, that’s the time to shut off the circuit breaker from the campsite power and get an electrician to double-check the outlet ground and polarity. Don’t bet your life on a faulty connection.

Using a Meter

After you’ve tested the campsite outlet for proper polarity (Part III of this series), powered off the circuit breaker and connected your RV power plug, now is the time to turn the circuit breaker back on and confirm that your RV is safe from a Hot-Skin voltage.

To use a standard digital voltmeter such as the one we learned about in Part II of this series, you’ll need to set it to measure AC voltage. Note that since a Hot-Skin condition will typically be less than 120 volts, the 200 volt or 750 volt AC setting [as pictured] will be fine.

Just like before, plug the black probe into the black COM connection on the meter and the red probe into the RED VOLTS connection on the meter. Remember, never plug into the 10 Amp connection, and never set the meter dial to amps or ohms. That’s for advanced testing only, and you’ll only blow out the meter’s fuse if you try to test for voltage that way.




Ready… Set… Test….

If you’re close enough to any metal going into the earth, such as the exterior of the pedestal power box or a metal water pipe, poke it firmly with the sharp tip of the black probe. You’ll need to punch through any rust or paint, so an exterior bolt or machine screw is usually a good choice. Now without touching the body of your RV with your hand poke the skin of your RV with the sharp tip of the red probe. Again, this needs to make connection to the metal skin of your RV, so if you want to avoid making little holes in your paint job pick a spot like the trailer hitch or a chrome door knob.

Next, while both probes are making contact you should read pretty close to 0 (Zero) volts. The National Electrical Code anticipates up to a 3 volt drop on the neutral conductor, so you can expect to read perhaps 1 to 3 volts between the ground and neutral of any loaded circuit. If, however, you read 10 volts, 50 volts or 120 volts, that’s the time to back away from the RV, turn off the circuit breaker, pull the power plug and immediately get the campsite electrician to find out what’s wrong. If he tells you that 50 volts on the skin of your RV is fine, demand your money back, break camp and get out of there. Do not let your family or pets enter an RV with a Hot Skin condition.  Also, it’s a good idea to alert your local RV association that a campground has a dangerous power condition. That way you help the next RVer, too.

Using a Non-Contact Tester

While a digital voltmeter is the gold standard method for testing Hot Skin conditions, it must be used exactly right or it can give you a false sense of security. Therefore, perhaps the easiest and best way to check for an RV Hot Skin is by using a $30 non-contact AC tester such as a Fluke VoltAlert. These testers look like a fat pen with a plastic tip and are available at hardware stores such as Sears or Lowes. Most have a blinking light and beeper that makes noise when the tip is held near an energized circuit. How do I know these things work? Well, I built a Hot Skin simulator that can energize the body of an RV with any voltage from zero to 120 volts at the twist of a dial. I’ve energized everything from a microphone to an Airstream to find the best Hot-Skin testing methods. Yes, it’s a bit Frankenstein, but this gear allows me to see how well the various test methods work. And the Fluke VoltAlert seems to work very well for Hot-Skin conditions as low as 40 volts.

To test for an RV Hot Skin just turn on the non-contact tester by pushing the power button quickly, which will begin to blink once every few seconds to show you it’s on. Then confirm the tester is working properly by poking it into a hot blade of the power outlet on the pedestal. It should beep at you and blink if all is well. Now, gripping the tester firmly in one hand while standing on the ground, move the plastic tip until it’s touching anything metal around your RV. This could be an aluminum screen door, the exterior of an Airstream or the steel of the trailer hitch. With a non-contact tester you do not have to punch through the layer of paint, rust or plastic. If your RV has more than 40 volts on the skin, the VoltAltert will light up and start beeping at you, even from an inch or more away from the surface of the RV.


Now, here are a couple of warnings about using non-contact testers to check for Hot-Skin conditions. 1) These testers need to have your hand wrapped around them to sense the earth ground; so if you hold them with just the tips of your fingers it’s possible to get a false-safe reading. 2) Non-contact testers need your feet to be near the ground to know the actual earth potential, so if you’re standing on a fiberglass ladder they won’t read properly. Additionally, since non-contact testers are looking for the voltage difference between the your hand and the plastic tip of the probe, if you’re standing inside an RV with a Hot Skin and you test your galley sink, they won’t indicate trouble when indeed there is. Therefore, always grip the non-contact tester firmly in your hand while standing on the ground outside your RV. And if your vehicle has as little as 40 volts of Hot Skin potential, the tester should alert you of the danger even without physically touching your RV. You can just slip your VoltAlert pen in your pocket and use it to quickly test any RV in the campground you might be visiting. It only takes a few seconds to test for a Hot-Skin problem this way, and you may save another RV owner’s life.

Outlets Re-visited

Since these non-contact testers are designed to check outlets for electrical power, they’re also a great way to confirm outlet polarity. If you remember what a typical AC outlet looks like, you can poke the VoltAlert into the tall neutral slot (no blink or beep), then the ground hole (no blink or beep) and finally the shorter hot slot (should blink and beep). It won’t tell you the exact voltage of the outlet like a voltmeter, but it will confirm if the polarity is correct and tell you if the ground connection has been floated and electrified by another RV with a short in its own wiring. This is pretty cheap insurance since you can never be too safe around electricity.

Quick Tips

  • Do the Hot-Skin test after you’ve checked campsite outlet polarity and voltages with a volt meter.
  • Perform a Hot-Skin test every time you plug into a new campsite or home power outlet.
  • If you ever feel the slightest tingle or shock from your RV, avoid all contact, shut off the AC power at the pedestal, and get professional help to determine the cause of the shock.
  • Even if you’ve stopped getting shocked from your RV because the ground is dry, the Hot-Skin problem has not fixed itself.
  • Be sure to properly maintain your RV electrical system and test all RV interior outlets for proper polarity and grounding.

Future Shock

Part V of this series will cover amperage and ways to calculate how much your RV needs BEFORE you plug into a power pedestal, so stay tuned.


After you’ve read this article at www.RVtravel.com, take a trip over to www.NoShockZone.org and send us your  comments and suggestions. We love to know how we’re doing with this important project.

Mike Sokol is the chief instructor for the HOW-TO Sound Workshops (www.howtosound.com) and the HOW-TO Church Sound Workshops. He is also an electrical and professional sound expert with 40 years in the industry. Visit www.NoShockZone.org for more electrical safety tips for both RVers and musicians. Contact him at mike@noshockzone.org.

New ground current tester update. More on this later.

RV Ground Current Tester Auto Probe Clip

65 Comments to “RV Electrical Safety: Part IV – Hot Skin”

  1. Proto says:

    Another great article, This information has always been out there but you have put it together in one place so that we can not only have the information but are able to do something with it.
    Great job

  2. Alan M Fisher says:

    Thank you for such logical and understandable explanations of electricity and electrical safety. Having taken college level physics many years ago, much of that information has “faded” until now. You have “recharged” my intellectual batteries, and for that blessing, I thank you. I have passed this information to many others. These articles are real “gems”. amf

  3. Andy Brown says:

    Enjoying your series on RV electrical safety. One point on ‘sitting on rubber tires’ inferring insulated from ground. Remember years back gasoline trucks had a static chain to ‘ground’ the static buildup from sloshing gasoline. Note that you no longer see them (for many years). The reason is modern synthetic rubber tires are not as good an insulator as was real rubber. So trucks and RVs are fairly well grounded, depending, of course, on the ground upon which it sits. This can allow ground currents up into RV from earth. Might comment on ground currents in your writing. Thank you for your informative articles. I, as a radio amateur am familiar with most things electrical , but can always use any knowledge that might help keep me alive.

    Thank you again, Andy, n6ijf

    • Mike Sokol says:

      While I think you’re correct about modern tires being more conductive than old rubber tires, I’m pretty sure that there’s so little leakage to ground through modern tire that you wouldn’t notice if your chassis is sitting at 120 volts above ground. I’ll do a few measurements on my Sprinter this week, but I’m guessing it will be in the tens of thousands of ohms to ground. Now that would certainly be enough conductivity to drain off any static charges from driving, but it’s surely not going to draw enough current to trip a 20-amp breaker, and I suspect it won’t even be enough leakage current to trip a GFCI breaker. But I’ll investigate all the circuit paths and leakage levels and see what the actual ground path currents would be. It will be fun to electrify my Sprinter up to 120 Volts and see how much actual current flows to ground through the tires. I’ll take pictures and report back later.

  4. Errol Littleton says:

    Thank you for your excellent articles. We are new to RVing and welcome all the help we can get. We have a Jay Feather with aluminum frame and fiberglass body. Where would you place the second probe instead of the side of the trailer since it is not metal?
    Thanks again, Errol

    • Mike Sokol says:

      The trailer hitch or a lug-nut on a tire is a good place to test for hot-skin voltage. It’s really the trailer frame that’s energized and the RV skin just goes along with that same voltage.

  5. […] his fourth installment, Sokol explains RV Hot-Skin conditions. So what exactly is a hot-skin condition? Sokol says this […]

  6. Mel Johansen says:

    Recently at a campground the 50 amp service was only putting out 196 volts. The meter read 109-111 volts. I have a surge protector and want to know if this is an ample situation for my motor home.

    On another note, the ice maker in the refrigerator will work for a week or so and then starts to trip the GFI. After that I have to unplug the ice maker for the rest of the trip. I even used an extension and plugged it into another outlet. Any ideas?

    Thank you.

    • Mike Sokol says:

      Well, I suspect your 50 amp service is running 2-legs of a 3-phase service, which at full voltage would measure 208 volts from leg-to-leg. That’s because of instead of your two hot legs being 180 degrees out of phase like in your home, they’re only 120 degrees apart. That’s OK since RVs typically don’t have anything powered by 240 volts anyways, just a bunch of 120 volt appliances run from one leg or the other. Your RV is really seeing 110 volts on each circuit which is a little low, but certainly within reason. Can you supply the name of the campground and I’ll contact them to verify my theory?

      For your ice maker, I wonder if the GFCI is being tripped by water dripping on circuitry somewhere inside the ice maker itself. That would allow 120 volt current to flow from the hot wire in the ice maker to the fridge chassis ground, and your RV chassis ground is dumping the current to the safety ground, which is exactly what it should do. But anything over 6 milli-amps of ground fault current will trip the GFCI breaker, which is exactly what it’s supposed to do. I would carefully inspect the ice maker for any torn gaskets that are allowing water into the electrical motors and such. If this is within warranty, I would simply ask for a new ice maker. In any event, please report your findings….

      Mike Sokol

  7. Brian Cloke says:

    Hello Mike.
    Thank you for a most interesting series on RV safety. I have been reading Part four Hot Skin.
    Ready, set,test.
    Using digital meter test. National electrical code allows 1 to 2 volts as being safe. If however you read 10 or 50 or 120 it is time to pull the power plug.
    Using non contact tester.
    The Fluke volt alert works very well as low as 40 volts. If your RV has more than 40 volts on the skin it will alert you to that fact. My understanding of this then is. If the skin of my RV shows less than 40 volts the Volt Alert will not respond or light up. Therefore using National code of 1 to 2 volts as being safe and any voltage above that as being dangerous I would conclude that the Volt Alert would lead me to think the RV is safe when it is not.
    If this thinking is correct it makes the Volt Alert a deceptive tool to use.
    Please enlighten me if I am missing something here.
    Thank you.

    • Mike Sokol says:


      Thanks for your thoughtful comments. In fact, the gold standard way to test for an RV hot skin condition is with the probes of a Digital Voltmeter poked between the chassis of the RV and a solid earth connection. Unfortunately, nobody does that type of test unless there’s a known shock problem they’re troubleshooting.

      The idea of using the Fluke VoltAlert came to me when I realized that most high-impedance RV hot skin conditions do indeed go up to around half of the line voltage (60 volts), while most low-impedance hot skin conditions go to full line voltage (120 volts). Also, many hot-skin conditions I’ve had emailed to me are intermittent and will come and go depending on which way you twist a power plug. Since the lower AC voltage threshold of electrocution is around 40 volts, the fact is that the VoltAlert will show you any potential “LETHAL” hot skin voltage of 40 volts or more.

      It’s not the ultimate test tool since it won’t measure chassis to ground impedance, nor will it give you an actual voltage reading. A VoltAlert just beeps at you and lets you know that touching the RV and the earth at the same time could be deadly. But it’s a simple, non-invasive test that anyone can do safely since there’s no need to touch the RV at all. I’ve had emails from octogenarians who now test their own RV’s and any other RV before they step into them, and a number of them have found hot-skin conditions which they avoided. And I’ve had an email where this non-contact test was performed after plugging their RV into a relative’s garage power outlet while visiting, and the mis-wired outlet energized the RV to 120 volts. I also had an email from someone who did this test on an old RV he was refurbishing, and when it beeped at him he measured the actual chassis voltage as 120 volts. He decided not to take his kids camping that weekend until he found and fixed the problem. He was grateful for the test since he had no idea his dog-bone adapter had a corroded ground pin which broke off inside the plug. And something as simple a a broken dog-bone adapter could have killed him or his child.

      So I’m sure this simple non-contact test has saved dozens and perhaps hundreds of RVing families from shocks and possible electrocution. And many RV technicians are now using it as a quick check on every RV they plug in. No, it’s not the ultimate test, but it will save lives. And it’s only $25 or so.

      Mike Sokol

      • Brian Cloke says:

        Thank you Mike for that explanation of the Fluke tool. As an aside. Many years ago when I was an apprentice in England a man was killed whilst working on a car by touching 12 volts. So by national code standards anything above 1 to 2 volts is still valid. Maybe fluke could come up with a tool that could read a lower voltage.
        I guess that a fluke is in my near future.

  8. […] avoided if you have an understanding of how the RV electrical system work. Check out Sokol’s fourth installment discussing the hot-skin condition. For more information about your RV’s electrical system, […]

  9. dieta says:

    Larger Motor homes and travel trailers may be equipped with a 50-amp power cord that has 3 #6 wires for power and 1 #8 wire for ground. This power set up is said to have 2 legs, (or circuits) of 110 volts each. The plug is the now standard 4 prong 50 amp 240 volt type found on modern electric ranges. All kinds of power adapters are available for this plug configuration, the most important thing to note is that most adapters, dog bone or other simply put the same 110 volt power from the 110 volt wall receptacle on to both legs, (circuits) of the power cord. This limits total usable power to the power available at the wall receptacle or outlet. 50-amp service can be connected to a properly wired 50-amp 240-volt receptacle, which will utilize the 2 legs of 110 volts. Typically there is no 240-volt electrical equipment installed in production RVs until we get into the bigger rigs, Bus conversions, custom units, etc. So for the most part we see 110-volt washer dryers, air conditioners, and electric cooking appliances.

  10. Elmer Bulman says:

    Something often overlooked when the RV has an OPEN ground wire but connected to a 120VAC 2 wire connection. In this configuration the floating ground/chassis can assume a float level as much as 60 VAC because of the coupling capacitance of the RV 3 wire circuits. This capacitance between the 3 wires is always there but the leakage current is less then the trip level of a GFCI, it only shows up as a problem when the GROUND conductor is open/floating. I have measured the capacitance at the male pins of the 30A plug on our Class C MH at about 0.037 (H to G) and 0.040 (N to G) microFarads which amounts to be about 66 KOmms at 60 Hertz. At 120 VAC this amounts to about 2 milliAmps where a typical Class A GFCI trips at 6 milliAmps.

    • Mike Sokol says:


      You are correct. And if you use a high-impedance volt meter to measure something like a crock-pot without a ground pin on its power cord, you’ll find that it actually have about 60 volts on the chassis. This isn’t dangerous to touch only because the fault current potential is so small. However, an ungrounded refrigerator or microwave can develop a much lower resistance internal fault that can source many mA or even amperes of current externally. Plugging that appliance into your RV’s electrical system will “reflect” the appliance’s hot-skin condition to the skin of the RV UNLESS the RV is properly grounded to the house or pedestal’s safety ground.

  11. Drew says:


    I enjoy all of your electrical safety articles- keep them coming! You are very specific and the articles contain the right amount of detail so that everyone can understand.

    Thanks again,


  12. Scott says:


    We just bought a used 2006 Jay Flight 26BH travel trailer. The other day as I was cleaning the unit up I could have sworn I was getting zapped a tiny little bit, my wife tried touching the door frame where I had touched it and nothing. Tonight though it was definite, I Googled it and found your site, boy am I glad I did. I took my no touch tester out to the RV and it lit up like a Christmas tree. I immediately unplugged the trailer and of course the tester doesn’t register anything now. I’ve tried multiple plugs in my home all with the same result, I refuse to believe all of the plugs I tried are wired wrong. Based on what I’ve read (I wasn’t using an extension cord) it must be my shore power cord or the 120 V adapter?? Does this make sense? I will be talking to an RV tech but I want to have as much knowledge on my side as I can. Hopefully it is as simple as changing the adapter or cord.


    • Mike Sokol says:

      I think that many (if not most) RV hot-skin conditions are caused by broken dog-bone/pigtail adapters, but you could have home wiring problems as well, depending on its age (pre-70’s is the worst). So at the very least, test your home outlet with a 3-light outlet tester, and follow up using your non-contact voltage tester. Here’s a video on how to test your home outlets for polarity: http://www.youtube.com/watch?v=jF3Ntoa8ab8

      Then I suggest you simply buy the best dog-bone adapter you can find and see if that corrects your problem (I’ll bet it does). The cheap/import molded adapters are notorious for the ground breaking internally, which is the primary suspect. Try this and let me know how it works.


      • Scott says:

        Hi Mike;

        My electrician buddy came over tonight and we tested the plug among a few other things, the trailer was sitting at 34 volts when energized! Turns out it was the adapter, the ground contact on the female side of it was splayed out a bit, so it actually created an intermittent Hot Skin situation. When we first started our investigation the trailer was not energized…..what the heck? Tested plugs, extension cords etc. As we were trying things the trailer would become energized and then not and so on because as we were un plugging and plugging the cord to the outlet the adapter would get “jiggled” and make contact then not. I got a cheap adapter for the time being as there isn’t much for RV products in my neck of the woods. I will get a better quality one when I can and keep the cheapy as a back up. Anyway, all things are good now, thanks very much!


      • Shannon Oswald says:

        I found your website through Google search because I was experiencing a hot skin condition with my own recently purchased RV. Come to find out the source of the problem is my garage electrical outlets, most of them do not have the properly wired ground pin, although they’re all three wire outlets. So when I connected my extension cord in the garage outlet and snaked it out to the Shoreline adapter and plugged in the shoreline of the RV that action electrified the skin of my RV. It didn’t become obvious until I was working near the generator and I got shocked… the generator was off at the time. Then the next day I started working on replacing brake pads and I got shocked while touching the lug nuts. That’s when I knew I had a problem. Through reading your article and some of the tips to and from other posters, I discovered that simply a missing ground wire on a home 110 volt 3 wire Outlet through the extension cord and through the electrical system of the RV is enough “?capacitance charge?” to present what I measured to be a 40 volt potential on the skin of the RV. I stuck the negative probe of my multimeter into the dirt and the positive probe to one of the lug nuts and I read 40 volts, scary. I’m happy to report that I moved the extension cord to a properly wired Outlet and my RV is no long externally electrified. Thank You.

        • Mike Sokol says:

          Very good. But it’s not really a capacitance charge causing the hot-skin voltage. Virtually every appliance in your RV leaks a little current to its chassis/ground. Add up enough of them (microwave, inverter, converter, entertainment system, computers, surge strips, etc…) and the voltage can easily rise to 1/2 of the line voltage. So 60 volts AC on a non-grounded RV chassis/skin is not uncommon. Most of the time this is a low-current leakage of maybe 5mA or so. But it can easily turn into a high-current leakage if you don’t have a ground wire on the shore power to drain it away. And that’s when it can become deadly.

  13. Jason says:

    Just wanted to clarify, a non contact voltage tester does NOT require you to act as an earth ground (some older models may have required this, but I haven’t seen or owned one since 2005 that required this). The whole unit is plastic, thus being an insulator, and runs off of 1 or 2 AA or AAA batteries, depending on which model you get. It functions by reacting to the magnetic field created when electricity is present in a conductor (wire, rv frame, etc.). I am writing this to help make sure you are giving the best information to people. The articles are great and I appreciate you writing them.

    • Mike Sokol says:

      Well, any Non Contact Tester does not operate on a magnetic field. If that was so, they would only work on circuits with current flowing. Actually, they work by capacitively coupling both to the circuit being tested (via the tip) and the body of the tester (via a small metal plate inside). Both the tip and body of the NCVT tester are indeed insulated, but the capacitance coupling allows AC voltage (60 Hz) to be detected by the very high impedance discriminator circuit. Essentially, it’s listening for “hum”. Now earlier NCVT’s didn’t have a very large sensor plate and required a hand to encircle the body of the probe for the earth coupling. But later model NCVT’s have a much larger internal capacitor plate in the body of the tester, and thus will beep when inserted into an active circuit even without a human hand on the body of the tester to add extra ground-plane capacitance. But there must be a ground plane link of some time for a NCVT to beep. For instance, if you’re standing inside of an RV that has its skin electrically energized (hot-skin), then pointing your NCVT at the door frame will NOT cause it to beep. That’s because both your hand around the body of the tester and the tip of the tester are at the same electrical potential. But standing inside of a hot-skin RV and pointing a NCVT at the ground outside WILL cause it to beep. I’ve tried this many times and confirmed that’s how it works. Also, the NCVT manufacturers themselves warn you that if you’re on a very tall fiberglass ladder doing a test, then your body/hand and thus the capacitive sensor plate in the body of the tester can be elevated high enough above the earth’s ground plane that your NCVT can fail to beep on a live circuit. I’ve tried this with an 8-ft fiberglass ladder and everything still worked, but perhaps standing on a 16 ft fiberglass ladder could de-couple you from the earth enough to shut down your NCVT tester.

      I’ve discussed this at length with the various NCVT manufacturers, and this is how it all works. Not magnetic, but rather capacitive coupling.

  14. Dbm says:

    I plan to install an onan Microlite 2800 in my van. The generator has a pigtail of three wires, green – white – black. I plan to run these wires to an outlet. Then I plan to plug a cable into that outlet and feed a breaker panel. For shore power I plan to have a second outlet that is supplied by a 30 amp male plug mounted in the body of my van. To use shore power I will unplug the supply cable for the breaker panel from the generator outlet and plug it into the outlet wired to the body mounted plug. My question is were should I bond ground and neutral? My thought is that I should not do the bonding in the breaker panel but I should do it in the outlet being supplied by the generator??? Correct?


    • Mike Sokol says:

      That’s correct. You must NEVER do a Ground-Neutral bond in your RV’s breaker panel. But you’ll want the Ground-Neutral bond in your generator. If your generator is already G-N bonded, then it should work as you describe. If your generator is NOT G-N bonded already, you can bond it in your Generator outlet as you planned.

      The key is that your RV’s electrical system mush have an isolated Neutral, and either the generator or the service panel of the shore power it’s plugged into will supply the G-N bond from ONE point alone.

  15. […] frame becomes electrified and very dangerous. For more information on this please check out the No-Shock-Zone website. They have many terrific articles on RV electrical safety including how to use the Non-Contact […]

  16. Susan says:

    Is the following non contact RV hot skin tester with LED light the best/suitable for a 2014 Class A Itasca 27N motorhome ? Fluke LVD2 Volt Light

    Also saw says operating temp max 50 Celsius (82F) – does this mean it wont work if temp 100 degrees ? Had 2 weeks of this temp last summer.

    I am not very electrical knowledgeable and don’t want to carry light and tester. Thanks

    • Mike Sokol says:

      Yes, that model Fluke tester should work just fine. And your temperature numbers are off a bit since 50 degrees Celsius is actually 122 degrees Fahrenheit. So unless you’re camping in Death Valley on a really hot day, all will be well.

  17. JTT says:

    My wife and I are waiting on the arrival of our first RV (29′ TT) and I have been gobbling up as much info as possible on RVing. I saw the news about the young boy killed by a hot-skin condition and started researching it since I have two young daughters and wish to protect them from such an event (among others). The articles you have written are great and very helpful for someone like myself who has a healthy respect for electricity, but a limited understanding of it.

    You mentioned in part IV under “Ready-Set-Test” that one should look for metal entering the ground (power pedestal, water pipe) and place one lead on it and the other lead on the RV. Since the test leads are only 10-12 inches long, how do you go about doing this if no metal entering the ground is close enough to the RV for the leads to reach both objects? This may be a dumb question and I’m probably missing the obvious, but…?

    • Mike Sokol says:

      For quick earthing tests I stick a long screwdriver in the ground. But even then you have to be careful not to poke through any underground wiring or plumbing at a campground. They often don’t bury the wiring as deep as code now requires. That’s why I’m an advocate for using a Non Contact Voltage Tester (NCVT) for doing quick hot-skin checks. If you do find a hot-skin voltage that way, then it’s time to establish a ground connection for further testing. But being sure that any test ground is actually at earth potential is a real problem, even for electricians and engineers. See my video on how to use a NCVT to check for an RV hot-skin condition at http://www.youtube.com/watch?v=Y8h64X33aKg

  18. nacole says:


    I’ve read (and reread) the article and appreciate the information but, have to say… still a bit confused. We want to make sure that are family is safe while camping, so we want to make sure that we buy the CORRECT testing instruments. We have a 2015 Jayco Whitehawk with 30 amp service. We purchased a Surge Guard surge protector however, I don’t believe this will protect you from a “hot skin” situation. Am I correct? I think we need to purchase a Fluke non-contact voltage detector however, I am confused on which one is the best as Amazon has several to offer. I am coping the information from their website as I have NO idea what any of this means:

    Fluke 1LAC-A-II Low Voltage Detector, 1000V AC Voltage 20-90V
    Fluke 1AC-A1-II VoltAlert Non-Contact Voltage Tester 90-1000V
    Fluke 2AC Alert Voltage Tester 90-1000V

    Which one should we buy? Do you actually use this tester on the 30amp outlet at the campsite? If so…I’m confused, are you actually tying to “plug” it in (so you touch) each hole in the outlet? And, when testing the camper, I understood you to say that you can stand on the ground and touch the hitch of the trailer to test…to confirm, you PHYSICALLY touch the trailer? I want to say no, as then you’d get shocked (and it is called a “non-contact” voltage tester)… sounds simple as I’m typing it but goodness do we want to make sure that we’re doing this right.

    Oh… should we buy one of these? Sperry Instruments GFI6302 GFCI Outlet Tester ( believe you plug this in and it will tell you if a basic outlet is wired correctly inside the camper and at the power box at the CG)

    Mercy… very basic questions, I apologize. Thank you, so much, for your time and advise.

    • Mike Sokol says:

      You can use a standard 90 to 1,000 voltage range NCVT such as the Fluke 1AC-A1-II VoltAlert Non-Contact Voltage Tester 90-1000V for testing your RV for a hot-skin condition. If it has as little as 40-volts AC on the skin/chassis, this tester will beep and alert you. It’s safe to actually touch your RV with this tester even if it IS energized to 120-volts since these testers are plastic and rated to poking them right on a 1,000 volt wire. While something like the Sperry outlet tester will do basic wiring checks, it can’t tell you if there’s a hot skin condition. Here’s a video of me testing a 40 ft RV with various hot-skin voltages I created on it. Kids, don’t try this at home…. https://www.youtube.com/watch?v=Y8h64X33aKg

      And here’s why 3-light testers such as the Sperry Outlet Tester you mentioned can’t identify all mis-wiring conditions. http://ecmweb.com/contractor/failures-outlet-testing-exposed

      • nacole says:

        Thank you… very much.

        Last year, we considered purchasing a generator (for our home). The manufacturer strongly advised us to ground the unit by driving a stake (copper I believe?) 4-6 feet into the ground and then connecting a wire from the ground to the unit. Would this process work to ground a camper? If so, I wish all CGs would be required to follow this process at each site. I can’t imagine that it would be terribly expensive for the CG to do, and this way each owner could safely ground their camper. Maybe that wouldn’t work though? This topic, “Hot Skin” is so frightening for us!

        Above you show a Fluke Voltage testing testing an outlet. Do you use this same tool/process to check the 30 amp outlet at a CG? I know that one time we tried to plug in with our surge protector and it would not let us (we kept getting an error code) so I’m wondering if the surge protector was checking the polarity and found something wrong? I can call the surge protector’s manufacturer on that. The 50 amp outlet was fine (we used a converter).

        Last question: Once you’ve connected your trailer and tested for hot skin and everything is good…. I remember you saying that it can still become energized (at any point??) and shock you. Mercy that is scary! So I guess the best rule of thumb, is to test your trailer every time you get in? Or is the largest concern when it’s wet outside? IF the Fluke devise tells you, that you have a problem… is it then safe to go over to the power box and pull the power cord from the camper?

        Thank you again. This topic is so incredibly important. THANK YOU for telling us!

  19. Rodger Schuester says:

    1) My understanding is that a non-contact voltage tester can produce a false positive reading. I’m wondering what situations would cause that.
    2) Recently I was at an RV dealership and my voltage tester lighted up on one of their rvs. Just below the steps were a couple of 50 amp cords. Could the reading off the steps have been a false positive produced by capacity coupling off the two power cords?

    Thanks, I have really enjoyed your articles.

    • Mike Sokol says:

      Was this RV plugged into shore power, or was it simply sitting next to the 50 amp cords? If it was actually plugged into shore power and you had a Non-Contact-Voltage-Tester start beeping close to the chassis, then there’s a VERY high probability it was a real hot-skin condition that would be dangerous. I hope you alerted the dealership to that situation.

      However, I’m assuming the RV was NOT plugged into shore power and was simply sitting close to the power wires. If that’s the case, then while the RV chassis could be biased close to line voltage, the potential fault current would be very low (micro-amperes) and not dangerous. However, I wouldn’t call that a “false” positive, since the chassis really IS at an elevated voltage, so the NCVT is reporting its actual voltage condition.

      Most of the public doesn’t understand that this exact same thing occurs every time you drive under a power line… the voltage on your vehicle will elevate to hundreds of volts for a second or so, then drop back to earth potential. But again, the possible fault current is so low that any voltage would be drained away by testing with a regular meter or touching the body of the RV with your hand.

      One interesting side fact is that parking a long and tall RV directly under low-hanging, high-voltage lines (they can be 250,000 to 500,000 volts or more) can induce a pretty high voltage into the RV’s chassis and “skin”. In that particular instance, it’s enough current so that you can feel it like a fence charger. All electrical line-men know this and are careful to jump clear of their boom trucks when parked under high-tension lines. They’ve all been bitten by this induced voltage, but again there’s not enough current to be dangerous since it’s only a few mA (milli-amps).

  20. Gregory says:

    Good Afternoon: I scanned over many of the posts. I have not found a post that reflects my problem – completely. My situation – When I plug into a properly grounded ( non-GFI ) shore line, all of the 120VAC circuits work properly. When I check VAC from interior outlet to door frame- I have a HOT-SKIN situation. NO shocks. When I plug into a properly grounded GFI shore line, the power is interrupted by the GFI. I Tested the circuit by using a ground cheater – GFI shore line does not trip. BUT NOW I have created a SHOCKING HOT-SKIN situation. I have diligently looked for the interior circuit that is touching the trailer ground – NO success. What other causes could be resulting in the HOT-SKIN.Thank you for your response.


    • Mike Sokol says:

      Any appliance with a ground plug has a certain amount of internal leakage from the line to the chassis, and that’s sometimes enough to trip a GFCI or create a low-current hot-skin condition if no ground wire is in place. The best way to find this is to turn off all RV circuit breakers and be that it doesn’t trip the GFCI. Then flip on the circuit breakers one at a time until the GFCI does trip. Once you isolate which circuit breaker line causing the problem, you can troubleshoot further. For instance, many microwave ovens that have some age to them will have internal line-to-chassis leakage in their power transformers. Also be aware that many inexpensive “surge strips” with MOV devices (like the kind you can buy at any big-box store for $10) will leak 2 or 3 mA of current to their ground wire. So while one surge strip may not reach the 6 mA trip poing of a GFCI, two plugged in together in your RV can cause an external GFCI to trip.

      Whatever you do, don’t leave the ground-lift “cheater” plug in place, since it can indeed create a deadly hot-skin shock hazard.

  21. Ryan says:

    I spoke to my RV dealer about feeling a small shock when working underneath the vehicle several times and they never could tell me what to check. Tingling but VERY uncomfortable. Felt this tonight on the frame while standing in water and got fed up and found your website. Used my non contact tester and it lit up on all metal on the RV. Can’t tell you how much I appreciate this website as I found my problem in the garage wiring I was connected to. I will carry my NC tester with me full time in the camper to check this from now on everywhere.

    Thanks again,

  22. Lou Tylee says:

    Thank you so much for your discussion of ‘hot skin’ – I recently got a shock touching my small trailer and found out I had a bad extension cord. A question – I use a surge protector between shore power and my trailer. The protector claims to detect lack of power, reversed polarity, open neutral and open ground conditions (using a series of green and red lights). Can I assume if the protector says I have power, correct polarity, no open neutral and no open ground that I am good regarding hot skin. Or is it still prudent to do your test?

    Thanks …

    • Mike Sokol says:

      Take a look at this article I wrote for Electrical Construction and Maintenance Magazine (EC&M) where I introduce the idea of an RPBG (Reverse Polarity Bootleg Ground). While an RPBG should be uncommon at campgrounds, they happen surprisingly often in old basement and garage outlets inside houses built prior to 1960. http://ecmweb.com/contractor/failures-outlet-testing-exposed. So plugging into your friend’s garage power while camped in his driveway could be dangerous.

      Currently, standard test gear and methods cannot detect the hot-ground of an RPBG. And plugging your RV into one will certainly energize the skin and chassis of your camper to a full 120-volts with circuit breaker current of 20 or 30 amps. Also, even if your surge protector give you the all clear, it’s still possible for your RV to develop an open safety ground internally due to vibration or corrosion. That’s what I think that using a simple NCVT to test the chassis/skin of your RV after you plug it into shore power is a great safety check.

      And, of course…. any time you feel the least little shock while touching your RV means there’s something wrong with the grounding system of your shore power. It could be anywhere from the pedestal to an extension cord or any dog-bone adapter in the power line.

      Mike Sokol

      • Lou Tylee says:

        Thanks for your response. I will always do the test … when I go to Amazon to get the Fluke 1AC-A1-II tester, it says it is rated for 90 to 1000 V, yet you claim 40 V. They also have one rated for 20 to 90V. Which should I be getting?


  23. Kim F says:

    Which one these testers do we need for our fifth wheel? There are three options offered on Amazon, and I am not sure which one is best. I read that as low as 40V is unsafe, so I assumed the 20-90V would be the correct choice, but I saw you mention in a comment above that the 90-1000V would detect 40V also. There is not much price difference, and I want to get the one that will work best for us. Thanks for your help!

    Options on Amazon:

    Fluke 1LAC-A-II, 20-90V or
    Fluke 1AC-A1-II, 90-1000V or
    Fluke 2AC, 90-1000V

    • Mike Sokol says:

      The Fluke 1LAC-A-II is the best for a hot-skin test only, and it will detect a hot skin down to 20 volts. However, it’s too sensitive to use on an outlet to differentiate the Hot and Neutral sides. If you want a tester for checking both hot skin down to 40 volts as well as checking for outlet polarity reversal, then the Fluke 1LAC-A-II is the correct one. Or Klein makes a dual-voltage tester called the NCVT-2 http://www.kleintools.com/catalog/electrical-testers/dual-range-non-contact-voltage-tester which will detect a hot-skin down to 20 volts, and can also be used to find hot/neutral polarity reversal.

  24. Scott Van De Walle says:

    Hello, I am getting shocked when I touch anything metal on the outside of my mother’s Rv. This just recently has started, after no incidence the last three years. It first happened when I washed the trailer and touched around outside, metal framed windows, and the front door. This happens only when wet. But i live in Florida, and it rains often. To stop the shock, i took a ground wire and grounded the frame to a ground rod. This has only temporarily solbed the no-shock issue. Is the problem in a electrical outlet inside? I cannot receive emails currently, and was hoping you could help guide me through this wonderful.page of yours ☺ Thank you for your time,
    Sincerely, Scott

    • Mike Sokol says:


      The thing to be aware of is if you get any appreciable voltage between the earth and the frame of your RV, then you MUST have a compromised EGC Ground wire (the ground wire of your RV’s power cord) or a lost ground in the outlet you’re plugged into. No ground rod should ever be required to “ground” your RV. So you need to check all extension cords and dog-bone adapters to make sure the ground is solid, and be sure that the outlet you’re plugging into is also properly grounded. A ground rod really doesn’t “ground” your RV. That must be done through the “ground” wire in the shore power cord and any extension cords, etc…

      Give me the layout of how everything is plugged in and I can offer more information.


  25. […] A simple little device to use for any RVer who hooks up to a power pedestal. It is very easy to use. With it you can safely check the campground power outlet for any possible faulty wiring that could damage your RV electrical systems or cause an unsafe condition. It is one of the only ways you can check for a condition called “Hot Skin” where the RV metal frame becomes electrified and very dangerous. For more information on this please check out the No-Shock-Zone website. […]

  26. David says:

    Is hot skin a hazard with fiberglass body motorhome RVs, or only metal skin types?

    • Mike Sokol says:

      Everything metal on your RV is bonded to the frame, and will be energized by a hot-skin voltage. That includes your tow vehicle if it’s connected to the RV. So yes, it is indeed a hazard even with a fiberglass RV.

  27. Matt says:

    Mike, thanks for your awesome posts. Just confirming something I have seen referenced indirectly a number of times on your site and others, but am having trouble finding any direct references to:

    I have a shore power outlet that goes to a GFCI outlet. The shore power ground clearly connects to the grounding terminal on the GFCI. I believe it should additionally get chassis grounded, to prevent a “hot chassis”. Are there any negative implications for connecting earth ground (via the shoreline) to my truck’s battery negative (as that is also chassis grounded)?


  28. Kirk says:

    Mr. Sokol,
    I just purchased a new jayco jay flight. When I got it home, I plugged it in to a 15 amp outlet using a 30 amp to 15 amp adapter and an old extension cord I had in the garage. while checking out something under the camper, I touched a piece of the frame and felt a shock. This shock wasn’t painful, but still very tingly. The ground and I were both very dry so I’m sure this was why the shock was minimal. I immediately unplugged the camper shore line from the extension cord and checked the extension cord out. I discovered that the ground pin was missing. After reading your website it appears The missing ground was the issue. I went out and purchased a new extension cord and the problem was resolved. My real question is why is the frame electrified in the first place? I understand that the ground becomes a path to eliminate the hot skin condition but should voltage be there anyway and is this something a dealer should look at? After plugging the new cord in, I checked the frame with a non contact voltage detector and found no voltage (at least 40 vac or higher) I also checked all camper outlets and outlet in house I was plugged in to with a 3 light circuit tester and all checked out well. Is a missing ground the cause of all of this?

    • Mike Sokol says:

      Yes indeed, a missing ground is the cause of it. That’s because anything that’s plugged into a power outlet leaks at least a little current to its chassis. The amount of leakage current allowed is regulated by the National Electrical Code and Underwriters Laboratory. So your microwave leaks a little current. Your voltage inverter leaks a little. And even your cell phone leaks a little current. Each appliance might leak less than 1 mA of current, but remember it’s additive. So 1+1+1+1=4mA or whatever. The job of the ground wire is to drain away these small currents so they don’t shock you. However, they can also be larger currents, and it only takes 10 mA of current through you to be very painful. And just 20 mA current through you is enough to shock you to the point where you can’t let go. Around 30 mA current through you is enough to stop your heart. It’s all a matter of degree. While you’re feeling a tingle you won’t really know how much current is available until you’re shocked seriously or even killed (electrocuted). So never plug your RV into an ungrounded extension cord. It can killed you even if there’s nothing else wrong with the electrical system.

      • Kirk says:

        Thank you so much. You may have just saved me from a headache with a dealer service call and possibly my familie’s life. I have never heard of hot skin or even the potential of being shocked by an ungrounded camper, even if there is no electrical issues. I have many friends with campers and I’ll be sure to educate them as well.

  29. W. Knapp says:

    When I plugged my motor home into my new Honda EU2000i generator for the first time I got a small poke when I touched the door to go in. I haven’t used it since in the hopes you could help me with the situation. I have never noticed this situation when plugged into a conventional AC outlet. Hoping for a solution as we really need our generator for our motor home. Thanks for your time.

    • Mike Sokol says:

      If you don’t have a G-N bond at the generator, then you could possibly feel a tingle when touching the frame of the generator and skin of the RV at the same time. I think you need a G-N bonding plug in the generator which will tie all the chassis metal together and prevent any tingles.

  30. Gary Kendall says:

    Hello Mike,

    We recently towed our new camper back home after a season of normal use and now have an unexpected electrical problem. Our Progressive Industries EMS unit that I installed at the beginning of the season worked perfectly through the season, but back home now it is showing an Open Ground fault when we plug in to the separate 30-amp circuit we have for the RV.

    I contacted Progressive and one of their techs walked me through some diagnostics – voltage checks at the input side of the EMS showed 30-40 volts on the Neutral-Ground path and higher voltage on the Hot-Ground (both numbers added up to approx. 120 VAC); Hot-Neutral showed 120 VAC also. The RV outlet on the house circuit tested normally – 120 V across Hot-Neutral, 120 V across Hot-Ground and just above 0 V on Neutral-Ground. I checked the terminal connections on the shore line connector on the side of the camper and they appeared secure and undamaged; we’ve tried a second shore line cord with the same results. I also tested using our “dogbone” 30A-15A connector to a standard outlet plug on a different circuit and had the same Open Ground fault indicated by the EMS.

    Being pressed for time and unsure of what else to do we are waiting for our dealer’s service tech to check out the electrical wiring to see what’s going on. I’m interested to know what else we could have checked as well as what other possible cause(s) would create the Open Ground fault that the EMS is detecting. Any thoughts you may have are appreciated – thank you.

    • Mike Sokol says:

      It sounds like you have an open ground in your home electrical panel feeding that 30 amp and 15 amp receptacle. The Ground-to-Neutral voltage should read leas than 5 volts AC, even under heavy load. Measuring 30 to 40 volts between Ground and Neutral on your house wiring suggests you need an electrician to figure out what’s wrong with your home’s electrical system. The EMS is just doing its job and shutting down unsafe power.

  31. Tango says:

    Would a ground rod such as those used to provide ground in non-mobile homes prevent hot skin? I am talking about literally shoving a bronze or cooper rod into the earth that is connected to the chassis.

  32. HAROLD SANDLIN says:






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