We have just brought home (new to us) a 2015 Cruiser Aire fifth wheel. Plugged it into our outside 20A outlet and it trips the GFCI. I have isolated the problem to the 15A microwave circuit. I have unplugged the microwave and used a circuit tester to verify that it wired correctly. On this circuit there is only the circuit breaker, wire, and outlet. Should I assume the circuit breaker is the cause?

Have you also checked the 20A outlet source with your circuit tester before you have plugged in the trailer Shore Power cable or RV30A to 15A long adapter.... You want to see the two bottom lights burning for CORRECT from the source 120VAC as shown in this photo...Google ImageMost of the time the GFCI is tripped because of a bad ground wire on the source connection in your House/Garage 120VAC connection. Also the RV30A to 15A long adapter may be at fault with its ground pass through. If you are using an extension cord plugged into the 120V outlet before using the RV30A to 15A Long Adapter and your Shore power cable you need to check the extension cord as well with the circuit tester.Anything you plug into between the 120VAC source connection could be at fault before you plug-in the trailer Shore Power cable connector which could trip the GFCI breaker. Roy Ken

Yes, I have tested the source outlet with that same circuit tester and the two bottom yellow lights lit up verifying the outlet is wired correctly.If I leave the microwave circuit breaker off, it does not trip.

Have you unplugged the micro? It can cause a ground fault.A standard breaker isn't able to create a ground fault by itself.

Use an extension cord to connect the MW to your GFCI outside plug. Results?

Yes, I have unplugged the microwave and it still trips.If the outlet is wired correctly and the circuit breaker cannot cause the fault, that leaves the wiring. The kitchen is on a slide if that adds any clues??

GFCI | Good Sam Community

KD4UPL
Explorer
Jun 02, 2017
It is most likely in the wiring between the microwave breaker and outlet; or, at the outlet itself. It could be the black (hot) wire touching the ground. It could also (more likely) be the white (neutral) wire touching ground. Either will cause the GFCI to trip.
2naEagle
Explorer
Jun 03, 2017
There is a good chance that the White (neutral) and Ground are touching. If the plug for microwave is easy to get to pull the plug out and look at wiring. You can try taking the plug off and separating the wires. You can also look at the trailer breaker box and make sure the White and ground are not together.

Let us know what you find.
NJRVer
Explorer
Jun 03, 2017
If everything is ok with the microwave unplugged then the problem is an internal one with the microwave. Trips as soon as you plug it in, or, as soon as you turn the micro on?
Not unusual. Common with blow dryers plugged into bathroom GFI. One blow dryer trips another won't.

Plug something else in the micro outlet and see what happens or if you have another microwave plug that in.
Masscamper
Explorer
Jun 03, 2017
I checked for a junction box and / or wires under the slide. Saw no issues. Pulled the cover off the breaker box in the RV and found the wire for that circuit were tight and connected correctly. Tomorrow, I will remove the wires from the outlet and see if that fixes the issue.
2naEagle
Explorer
Jun 03, 2017
Masscamper wrote:
I checked for a junction box and / or wires under the slide. Saw no issues. Pulled the cover off the breaker box in the RV and found the wire for that circuit were tight and connected correctly. Tomorrow, I will remove the wires from the outlet and see if that fixes the issue.

Keep at it your doing all you can. Keep us posted.
Masscamper
Explorer
Jun 20, 2017
After a break from all the rain, the GFCI has stopped tripping at home. We have been out for a couple more weekends away and no problems there either. I'm still keeping my eyes open for the cause.
Etstorm
Explorer
Jun 20, 2017
Also, I have found that if you plug a GFCI device into a GFCI outlet it will trip.
Me_Again
Explorer III
Jun 20, 2017
So one of the main things a GFCI does, is measure that all current going out the hot is returned on the common neutral. So somewhere in the MW circuit it is leaking current on the hot lead. As you stated that the minute you turn on that breaker, the GFCI trips even without the microwave plugged. Moisture in a slide junction box or cable comes to mind.

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