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GFCI circuit abnormality?

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I recently noticed what I think is strange. I typically keep a circuit tester plugged into the wall outlet which is on a GFCI circuit. I do this because while on the inverter to power the residential refrigerator I want to know if the circuit trips while driving so I can pull over and fix it. Recently though I noticed that it shows a "CORRECT CIRCUIT" however when the rooftop A/C is running the tester shows "OPEN NEUTRAL". Has anyone else had a similar situation or perhaps this is normal? TIA and apologies if this is posted incorrectly

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The inverter provided 120v AC to dedicated circuits when shore power or generator sources are unavailable. 

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I recently had a wire in the junction box that is near the a/c air intake short out to  the box due to rubbing against the box.  Lots of vibration from the a/c.  It may have caused an intermittent loose connection of the neutral wire, triggering a fault.  Easy enough to check.  

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I would check for (loose) high resistance connection on the neutral wire. 

It's also possible that the waveform of the inverter is causing a false indication. That's more likely with MSW inverter than with pure sine types.



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Unless you own a High End Totally Electric coach with multiple batteries and multiple Inverters, there isn't any motorhome that I know of which comes from the factory wired to run rooftop AC's on Inverter/battery power. They are not even wired that way.

My Windsor is wired to power ALL outlets throughout the coach EXCEPT for the one duplex that was dedicated to the NotSoCold. I now use that duplex for other purposes. My two rooftop AC's are wired directly from the main power supply panel which doesn't go through the Inverter Power Panel.

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There are a few things to try before getting too far into troubleshooting what might be nothing at all.

1. Try a different type & model of circuit tester in the same GFCI under the same circumstances to see if reacts identical to the one you are currently using.

2. Plug your current tester into a different GFCI outlet to see if it reads similarly to the GFCI circuit in question under the same circumstances.

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I agree with Richard. BUT first, I would go back to basics and do a Voltage and Continuity measurement.

BTW....if you do some "LOOKIING", you MAY luck out and find that there are TWO loads or outgoing circuits on the GFCI. Mine had that. I found that ONE of them went to the Refrigerator (inverter) Icemaker outlet. I pulled that line and put it on the LINE side, so effectively, my Inverter Refrigerator Outlet was NOT GFCI Protected. There were NO OTHER downstream outlets within 6 feet of a water (ground) source, SO I rewired it and solved a world of problems. This has been cussed and discussed many times. If you had a Monaco Factory setup, there would not be a GFCI on the ResRefer....so look at that first....


The small terminal (blade) is the Line or HOT. The wider one is the Neutral and the Round is the ground.

Line (small) to Neutral (wider) should be a nominal 120 VAC.

Line to Ground should be 120 VAC

Should be ZERO VAC between Neutral and Ground.

Should be very low, if any, resistance (Continuity) between Ground and Neutral.

I was having an issue with the Magnum. The switch to inverter when you broke camp was flaky. THEN...I realized that the Setup on the Magnum was OFF. The values were all over the map. Had the wrong type of battery and such. THEN, there were times when I could NOT actually change or reprogram it. 

Talked twice to Magnum. They pulling the remote (phone cable) from the Inverter. This basically takes the Remote out of the circuit. THEN do a reset. This resets the INTERNAL electronics to "default" which is fine for a typical 4 bank (6 VDC) setup. The "Search" function is active, so you might get a blip and a Sat Receiver dish might reboot or you lose the microwave clock.

THEN....run it that way. BINGO....no issues on the switch from LINE (genny) to Inverter.

Therefore the remote was "flaky". They also had me look at a tech spec setting, but the results were inconclusive.

Therefore, I ordered a new remote. They told me which one was the latest Rev level for my inverter (it is a MS2012 PSW).

THAT might be the issue....OR, if you have a problem with the Charging or a connection and get a Low Battery Cutoff. A LBC (voltage drops below your set point), then the inverter shuts off and the there is a FAULT.  I did this recently during a battery exercise/load test. I THINK that you really need to do a RESET to clear the inverter and properly restart the system. I did that and also checked my remote setting parameters. THEY WERE FINE.

I would verify that I truly DID have an OPEN Neutral....and then chase that. BTW, if your GFCI is older than say 5 - 7 years, REPLACE IT. IT gets crotchety. Use a 20AMP unit and stick with the stock one....Magnum publishes a list of which ones to use. Cooper Wiring Devices got swallowed up by Eaton, so an Eaton Wiring Devices is what you need... I put one in in 2013 and it is still working great today...

IF that does NOT solve the issue and you DO have have an open neutral, you need to start trouble shooting and check the INCOMING line to the inverter....as well as the internal connections...

Good Luck... 

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