Community Forums

Dascro · 05-31-2010, 05:27 AM

Hello all,

I'm a new member and new to RV'ing. We just purchased a used 25 ft, 2003 Skamper that by indications appears to have been well cared for and in very good condition. All appliances, outlets, faucets, AC, ights, etc. were checked out before we purchased the trailer.

Which brings me to my first newbie question. Once we got the trailer home, I plugged it into a regular outlet in our garage using the 30 Amp adapter. While I was crawling around underneath getting more familiar with everything I touched a metal band that secures the plastic blackwater pipe to the frame. I got a little electrical shock. I used my meter and found about a 3V current at that band to ground. I also found the same 3V at other points on the trailer frame. No breakers are tripped, everything works fine and no GFI is tripped. Is this normal? If not, what is the problem?

eieioh · 05-31-2010, 06:50 AM

Welcome to the forums!

I am not an electrician. But, I will take a stab at answereing your question. NO! Voltage to ground is not normal. I am guessing there is a bad ground in your shoreline, adaptor, or house receptical. Without the ground lead this voltage will use the easiest path to ground, and that will be YOU and your loved ones. If the condition worsens and the potential increases, someone could get seriously hurt.

Now, This has only been my contribution and it was free. Consider the value of free advise.

Happy Camping!
ed

wa8yxm · 05-31-2010, 07:59 AM

3 volts current? Current is measured in AMPS not volts. However I do understand what you mean.

Check your ground lead.. Use one of these 3-light testers you plug in

Start by plugging in in the garage, then in any outlet in the trailer..

I'm guessing a ground is open somewhere.

mahon1993 · 05-31-2010, 08:31 AM

You should go and get yourself a plug in plug tester to test your AC outlets. They usually have three lights in them to indicate problems. You can get one pretty cheap at HD or Lowes. It's a handy tool to have. Also works great testing 20A plugs at campgrounds.
Greg

wa8yxm · 05-31-2010, 03:38 PM

I will add one note.. If the outlet you plugged into has an open ground,,, Of if the extension cord has an open ground a reading of 3 volts... Frame to ground, is actually less than what I'd expect... (Depending on just where the break is and a few other things) A high impedeance volt meter (And most are) could read as high as sixty (however even the slightest "load" (current path) between frame and ground will reduce that) A low end (Say 8.95 at the low price bin at the hardware store) meter might show 10 or less being lower inpedeance.. (Which by the way is better in some cases)

Dascro · 05-31-2010, 06:54 PM

Thank you all for the helpful information. Sorry about the "volts" and "current" mix up

. I do know the difference, but happy you understood what I meant.

I measured the 3 volts using a multi-meter. I do plan on following the advice and purchasing a three light tester for the AC outlet I'm using.

Again, thanks for all the help.

Dascro · 06-02-2010, 04:08 PM

As a follow-up and for future reference and help to others, I purchased the three light tester. The outlet I was using for power had the hot/neutral reversed. So that would be the problem at the trailer then, correct?

Again, thanks for the help.

Ray,IN · 06-02-2010, 06:22 PM

Dascro, welcome to irv2.com! Don't count on it being the ONLY problem. Hot/neutral reversed is a problem, and it will cause problems in the trailer. Once you have that corrected, test again with your meter for voltage at the same clamp you tested at first. If the voltage disappeared you found the problem, but- you should open your trailer breaker box and tighten every wire set-screw including ground wires, they loosen from road vibration over time, and/or a factory worker was lazy that day. Be sure to disconnect from shore power first!
I once had a MH with that issue, the problem was in the CG pedestal but my MH had a faulty ground too. My daughter discovered it exiting the MH barefoot.

Luv2go · 06-02-2010, 07:16 PM

I agree with Ray. The reversed line and neutral may not be the root cause.

If I were you, I'd tighten all the connections as he suggests (after unplugging the camper's cord, of course) and then check the connections using the resistance function of your meter. For example, the connection from the ground prong of the shore power cord plug to a receptacle ground in the coach, the metal bend around the blackwater pipe you were touching, etc.

You should get less than an ohm from any of these connections. If you do not then you can use the meter to find where the bad connection is, i.e. from cord to breaker box, box to camper frame, etc.

BTW, before measuring the grounds, short the meter leads together and note the reading. You may get a few tenths of an ohm with just the resistance of the leads. Subtract this to get the true reading (or if your meter has it, use the "delta" or "relative" button to zero out the lead resistance).

We had a similar problem in our old coach. One evening while visiting relatives in Atlanta (in summer and of course running the A/C) we smelled something coming out of our electrical panel, it also was quite hot. Turned out to be the neutral set screws were loose, so loose the wires got hot enough to melt the insulation!

Stewart

RV Mech Tech · 06-02-2010, 07:51 PM

Dascro- if you find you have a problem with the RV itself try this- shut off one AC breaker one by one to isolate the circuit involved- once you have found the specific circuit check to see if that circuit powers an outside outlet - any outside outlet should be downstream of a GFCI outlet and I have found two RV's last year with the outside outlets full of water and the GFCI that was upstream became defective because the owner kept pushing the reset button to turn it back on- this may be another posibiltiy with your RV - I always do a "hot skin" test on any RV I work on and you would be surprised at how many RV's have a similar problem- another possibility is that you have a pinched wire somwhere in the RV and it is conducting crrent into the frame of your RV- isolating the specific circuit is the first step- let us know what you find.

Dascro · 06-05-2010, 12:51 PM

An update. I now tried powering the trailer from a GFI outlet that I checked with the 3 light tester. Everything checked out good. When I plugged the trailer into the outlet it tripped the GFI in the building. I pulled the cover of the panel box in the trailer and all the connections are tight and look good. I crawled under the trailer and saw the connector for the neutral and ground seem to be pretty heavily corroded. Could this be the cause of the problem?

Thanks for any help.

Dascro · 06-05-2010, 01:50 PM

OK, another uodate.

Turns out the GFI outlet I was using was previously overloaded. We live on a small farm and the outlet is located in a shop portion of a building. My brother just informed me about that situation. Anyhow, moved to another outlet in a different part of the shop (again, proved out correctly with the 3 light tester). Everything powered up fine this time!!!

And since I now had power in the trailer, I metered across the main power feed in the panel box (hot to ground gave me 0 V; hot to neutral gave me ~120 V). Seems everything is OK on the main feed at least. I also checked the outside outlets with the 3 light tester and they checked out fine. The multimeter showed ~120V at the outside outlets too. I do plan on checking each connection in the panel box. But thats for tomorrow.

And lastly (sorry for the long post) how do you do a "hot skin test"?

RV Mech Tech · 06-06-2010, 12:49 AM

Dascro - a hot skin test is done when someone feels a shock or a tingle on any metal part of the RV - (door handle, window frame, outside metal skin etc.) - this indicates that a short to ground (the RV frame and metal parts) has occured and a high voltage current is now traveling through the metal parts of the RV ( the amount in amps will vary depending on the problem but if you feel even a tingle that's dangerous enough - it only takes 5 milliamps of current to stop the human heart) - if this occurs you put your mulitimeter on the scale for 120 volts and take the red positive + leed of your mm and touch the skin of the RV (outside metal panelling anywhere) and then take the black - leed and touch the ground - if current is going through the frame it will show up on the meter- if it does show on the meter then you can isolate which circuit it is by shutting off the breakers one by one until the mm drops to zero - you would be surprised at how many new RV's have problems like this - pinched wires, staples or brad nails going through and grounding (short to ground) on the frame, slidouts with no protection for the wiring or wiring routed the wrong way so that it will rub up against metal and be pinched when the slidout goes out etc. - in your case it sounds like the power source was at fault- also clean or replace all the corroded connections as corrosion = extra resistance and can cause overheating and a fire.