Originally Posted by stevebaz
Once you get the wiring straightened out in your trailer then I would also revisit the GFI in your house. Your trailer failing the GFI test at several campgrounds opens up the question why it didn't fail at home if there was a real problem. An improperly wired GFI is not protecting anyone.
Depending on the age of the GFCI, it is possible that it will not trip for all faults. Older GFCIs only tripped with a hot to ground (or anywhere besides the neutral) fault. Newer ones added a neutral to ground fault detection circuit.
If you have a bad water heater element or 120v electric element in the refrigerator
that faults to ground on the neutral end, this will trip a modern GFCI, but not an older one. Sorry, but I don't remember the date that the newer GFCI started to replace the older versions.
Since many do not have an account at RV.net, I'll add a copy of a post I made there on troubleshooting a GFCI problem:
"Actually, whether or not a neutral/ground fault will trip a GFCI depends on when it was made. The early GFCIs did not detect a neutral/ground fault - modern ones do.
The bottom line is that it should be possible to plug your RV into a GFCI protected receptacle without tripping it. If it trips, something is wrong, and it should be corrected. I know there are those that will give all kinds of reasons why it is OK, but it isn't.
If the fault is between a hot & the ground, it is fairly easy to find. Shut off all your secondary breakers, plug the RV into a GFCI receptacle & turn on the circuit breakers one at a time. If one of the breakers causes a trip of the GFCI, you have found the circuit causing the problem. Typical faults include moisture in a receptacle, a bad hot water or refer element, a bad appliance, or a loose connection (although a loose connection that causes a low resistance hot/ground fault should trip the breaker rather than the GFCI). If the problem circuit has individual appliances plugged into it, unplug all of them & plug them back in one at a time to identify the problem appliance.
If the campground GFCI trips with all the breakers off, you have a neutral/ground fault.
A neutral/ground fault is a bit more difficult to find because shutting of the breakers won't prevent the GFCI from tripping, so finding the circuit is more difficult. If your or anyone else has modified circuits in the RV, it is worth checking that the neutral & ground have not been intentionally combined anywhere in the RV. The only place the neutral should be tied to the ground is at the campground's service entrance. If you tie it in the RV, the campground (or home) GFCI will trip.
Ground/neutral faults can also happen unintentionally. Again, a failed hot water heater or refer element can cause a fault as well as water in a receptacle, a screw hitting a wire, etc. The problem is an RV will function normally with a neutral/ground fault when plugged into a non-GFCI receptacle. This may be why some feel there is nothing wrong. In a worst case situation, if the RV ground pin (or any part of the grounding system, RV or campground) fails, a neutral/ground fault will place the chassis & most metal in the RV at the neutral potential. This produces a shock hazard to any real ground such as the campground water pipe, the RV parked next to you, etc. It also causes another interesting problem - The neutral current is split between the neutral & the ground. Again, with a failed RV ground, you might receive a shock disconnecting your water line from the campground faucet!
Finding a ground/neutral fault involves digging into your breaker panel. If you are not comfortable doing this, leave it for an electrician. If you want to do it yourself, unplug the RV, make sure an inverter or generator
is not powering the panel, and shut off all the breakers, including the main. Disconnect the neutrals (white wires) one at a time (don't include the main). With a neutral disconnected and all the breakers off, plug the RV into a GFCI receptacle. If it trips, the problem is not that neutral. Reconnect it, & try another. Eventually,you will find the neutral that, when disconnected, prevents the GFCI from tripping. Follow that neutral to identify the circuit, and check the circuit for the problem. Again, this may be more than a non-electrician wants to get into, but I don't know a better way to find the problem."