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Old 07-18-2012, 09:15 AM   #1
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HELP, shell shocks when 110 on

So i noticed yesterday when working on the back of the AS that I was getting a tickle of a shock form the shell and bumper. Like a half discharged 9v battery. Then last night i got a little tickle from the front curve when I brushed up against it, about 1/2 what I got in the back.

Now it only does when hooked up to 110. So I figure it can be two things.

1. positive wire touching somewhere, but I would think this would short out a fuse.

2. bad ground. This could be as the ground wire connected to a bolt in the rear c-channel to the frame. But the frame is painted with por15 so it might not be getting a good ground.

Is there any other option that I am over looking?

I will try to clean the paint off where the bolt comes through or run another wire to a different part of the main frame.
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Old 07-18-2012, 09:31 AM   #2
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This could be dangerous.

Try to see this voltage with a meter from the shell to a shore power ground. If you can, then try to isolate and locate the short, maybe starting by shutting off circuit breakers one at a time and working back. Don't put yourself between this voltage on the shell and the whatever the trailer is parked on, especially if wet. If not familiar with electrical work, take it to service.

It could be something else not as serious, but be careful until you are sure.

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Old 07-18-2012, 09:56 AM   #3
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When you're on shore power, all appliances and outlets are grounded to a ground bus that is completely independent of the 12v ground. From there, the ground bus is connected to the green-insulated ground conductor in your shore power cable, and goes to earth ground from there. The 110vAC system is not supposed to be grounded to the trailer frame AT ALL. From the point of view of the shore power pedestal, the whole trailer acts like one big appliance plugged into the outlet.

Don't randomly start moving wires before you identify the cause of the shocks.

What you describe sounds like an AC ground fault, probably on a circuit that does not have GFCI. Because of the ground fault, the trailer's metal skin and frame are seeing current leakage, and it's forming a path to earth through you when you touch it. As dkottum said, it's dangerous. If it gets worse, it could be lethal.

Start at your circuit breaker panel. Switch off each breaker, one at a time, and use a circuit tester, not your body, to connect from the the bumper to earth. When you switch off the offending circuit, the current shoud go away, so no shocks. Check every circuit, including the GFCI-protected ones. If a GFCI isn't working to protect you from shocks, you need to know that, too.

Once you identify which circuit is causing the shocks, you'll have a better idea what to fix.

By the way, an energized trailer frame/skin is exactly why, when you run a portable generator, you're supposed to ground the generator to earth.
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Old 07-18-2012, 10:01 AM   #4
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Check the outlet you are plugged into first and make sure it is wired correctly and the ground is good. I always start at the source when trouble shooting electrical issues and work my way out. You can get an LED outlet checker at Lowes or HD or use your VOM. If you have not had problems with the trailer in the past that might be the problem. If you have a GFI outlet to plug the trailer into using a regular extension cord and adaptor it will be safer to work on, just don't try and run the AC. I think you have the right idea checking grounds. After the outlet, I would start at the breaker box and you can do this with the power off. There should be continuity between the box itself and the shell and frame. Pull the cover off the breaker box and make sure the green wire from the power cord is securely attached to ground lug and the white wire is attached to the neutral bus. Only the Black wire should be attached to the bus that feeds the breakers.
If all this checks out you may have a bare wire somewhere. Check a circuit a time .
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Old 07-18-2012, 10:05 AM   #5
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A open ground between your TT and your source or a reversed hot and neutral are a couple of common possibilities. In any event you are getting a warning that something is incorrect and must be resolved. There was a report not long ago where a barefoot youngster touched an RV and was killed.

Miswired outlets are not unheard of and I carry these to check an outlet before plug in when on the road.
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Old 07-18-2012, 10:07 AM   #6
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My 68 has a ground wire between the 120 v breaker box itself and the frame/shell. Don't know about newer trailers but 68's are grounded to the frame.
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Old 07-18-2012, 10:21 AM   #7
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It should be grounded to the frame and shell. Otherwise if a hot wire hit the shell it could have 120V on it. Sounds like some sort of ground loop problem. Make sure the hot and neutral have not been reversed on the shore power.

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Old 07-18-2012, 11:19 AM   #8
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It sounds to me like the hot wire (120 volt) and the neutral are reversed. At the source ( receptacle) or more than likely at the trailer.
Only back wires should be connected to the circuit breakers.
Only white wires should be connected to the neutral buss.
Only green or bare wires should be connected to the ground buss.
The neutral buss should not be connected to the chassis in any way. The neutral side of the 120 volt circuit is a floating neutral. It is only tied to the earth ground plane thru the power panel in your home or other source.
The ground buss should be bonded to the trailer chassis.
If the shore power cord has a removable end on it. It may have been wired incorrectly. If the plug is not clearly marked for the proper connection and it has brass (gold colored) and silver screws. The black wire goes to the gold colored screw and the white to the silver screw.
Check the ground plane as well. If it is wired correctly and the hot wire is connected wrong, it should trip the breaker in your home.
This is a dangerous situation! You need to resolve it. Until then, do not plug the trailer in.
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Old 07-18-2012, 11:26 AM   #9
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You have an open ground and reversed hot in your shore power cable or in the socket on the shore power side. The 120V is shunted to the shell through the reversed polarity light and the open ground allows the shell to stay hot without blowing a breaker. This light should be disconnected in all Airstreams.

This dual error usually happens, rarely, at trailer parks.

Just to be clear, this is a small bulb that is in a jewel cover in the shell somewhere near the rear street bumper. The bulb is connected betweeen your 120V neutral in the trailer and the shell. This connection provides the sneak path for the hot when the shore hot is reversed.

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Old 07-18-2012, 12:02 PM   #10
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Forgot about the polarity light. It was one of the first things I removed when I bought the trailer.
It was miss labeled anyway, AC current has no polarity. If anything the light should have been labeled "Ground Fault"
It was a safety hazard from the get go. If for some reason the shore power connection to ground was open and the hot a neutral legs were reversed, the light wouldn't come on. If the light did come on it was grounded, probably thru you when you touched the trailer. Even if it didn't conduct well enough for the light to come on, the 120 volt hot side would stand on the ground side of the bulb. That's why you get shocked. Even ever so slightly.
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Old 07-18-2012, 12:42 PM   #11
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Is the polarity bulb something that was installed only on vintage trailers? If you remove the bulb, do you cap the wire(s) to it or just leave the socket empty and ignore it?

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Old 07-18-2012, 01:05 PM   #12
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Our 67 started doing that a few years ago. Turns out to have been the original plug, which was one of the horizontal kinds (not the ones that have a 90 degree turn in them like modern plugs). I guess the stress of the years had caused it to crap out internally, allowing positive to get into the ground. New plug, problem fixed.

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Old 07-18-2012, 03:28 PM   #13
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This whole "shell-shock" thing could be a plus if you're parked in an iffy neighborhood. Maybe you could have a hidden switch that would be "wired correctly" in one position, and "hands off my AS" in the other....I'm kidding, of course, but something akin to this has crossed my mind a time or 2.
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Old 07-18-2012, 04:16 PM   #14
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Just get a few signs that say: "10,000 volts! Keep way!"

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