J. Wimbish, (Arlington, WA)
John, the problem could be located either in your RV or in the park wiring. It is important to know if the same GFCI, (ground fault circuit interrupter), on that pedestal trips when another RV is connected to it, or is it just yours? Also, is it possible for you to try another GFCI-equipped pedestal? Perhaps at another site? It is quite possible that single GFCI is weak or faulty, but it's also possible the entire park is miswired.
Here's what you can do; With the RV plugged into a source of 120-volts, check each receptacle in the coach with a voltmeter and a polarity tester. You may just find a receptacle with reversed polarity. Also, the GFCI in the RV could be wired incorrectly thereby allowing the "hot" lead to cross over to the neutral bus since both sets of wires connect to the GFCI in the coach.
With the coach plugged in, one set of conductors at the GFCI will indeed be "hot." The technician will use a voltmeter to determine the hot "line" set of wires and their proper connection to the GFCI. If that does not clear the problem, it will be necessary to perform a hi-pot test, also called an insulation breakdown test. When applied to the electrical shoreline cord, the hi-pot test forces high voltage back through the system and reveals if any leg of the circuit is faulty. Further troubleshooting can determine if a particular circuit is at fault or if one wire in that circuit is shorted. It sounds like a visit to your local RV service center may be in order.