View Full Version : Ground Fault Tripping

Richard and Rhonda
11-14-2008, 02:14 AM
I have never been able to plug my coach into a 20 amp GFI circuit in order to run the fridge and lights when parked in front of the house without an instantaneous trip of the GFI circuit. The folks who make some of the circuit boards, PMMI, offered to sell me the "fix" for several hundred dollars. It seems the lights that indicate voltage and especially polarity, bridge across the two hot legs and trick the GFI into thinking there is a fault.

I am happy to report that plugging it into a NON GFI circuit works just fine.

Dang, now I can't justify to the CFO, running a 50 amp circuit to the front of the house.

11-14-2008, 03:16 AM
richard, please remind me which boards you are referring to? the indicator lights i believe you are referring to in my coach are not done controlled by an circuit boards. i have replaced all the neons in my coach in the transfer switch and the front panel inside the coach.


Richard and Rhonda
11-14-2008, 12:54 PM
According to PMMI, it's tucked away right above the power cord. I have lights in three places. Power cord bay, at the transfer switch, and at the front panel above the driver, plus a light on the dash that indicates shore power.

11-14-2008, 05:31 PM
your coach must have a power control system very different than mine. i do have a power management system installed that is from EMS, but it is entirely independent from the indicator lights i am referring to. i have neon lights mounted in my transfer switch box (5 of them) that i have replaced and 6 more on the panel above the driver that show both legs of 120 and 220 and error and generator on. i replaced them as well. all of the neon lights i have replaced are not connected into any electronics and are purely indicator lights based on real power conditions.

i do have 2 pmmi boards in mine, one for the tank levels and another is the clock in the bedroom.


11-14-2008, 07:28 PM
Again differences in each coach as well as year to year. My system is most similar to Tom's but without the EMS. My power cord goes directly into the rear of the transfer switch and I am unaware of any PMMI board in that bay. I do have the lights on the manual transfer switch and the lights over the driver.

James Tuckness
11-20-2008, 03:49 PM
One possable reason your coach trips a GFI receptical is the ground and neutral wires are connected. This will split the return between the ground and neutral and show a inbalance to the GFI. New electrical code requires the ground and neutral be seperated.

417-866-0261 Call if you want more information.

James Tuckness
71 30'
4 years into restoration.

Richard and Rhonda
11-20-2008, 06:41 PM
Thanks James,

As far as I can tell the ground and neutral are not bonded at the main breaker box. Now, that doesn't mean they aren't somewhere else in the coach.

James Tuckness
11-20-2008, 08:49 PM
Try a ohm meter between the ground and neutral bar and see if there is a path.

My coach will do the same as you describe when pluged in to a GFI.


01-03-2009, 06:05 AM
My '76 also trips any gfi as soon as it's plugged in. Any further experience/explanations would be appreciated.

01-03-2009, 06:33 AM
I found that when my coach is plugged in a GFI 15 amp circuit, it also trips the breaker.

01-03-2009, 03:03 PM
An interesting side note (I realize we are talking here about plugging the motorhome in to a GFI outlet).....I have yet to find a single GFI outlet in my 1982 Newell...not even in the bathroom, or kitchen. On my previous 1987 Class C I had one GFI outlet located in the "bathroom", which was connected to the external electrical outlet, and I usually had to reset it every time I plugged in to shore power.

01-03-2009, 03:52 PM

my coach does not have any gfi breakers or outlets installed either. btw, very simple to do at the breaker or at the outlet.

my coach does not blow a gfi breaker in my house when plugged in. when michael was here visiting, we could not get his coach to stay powered when plugged into the same outlet as my coach is. it kept blowing the gfi breaker in my house.

i can only attribute mine to acting differently because the previous owner on mine put a microprocessor controlled power management system that checks incoming power and makes sure it meets spec before allowing it into the coach. that is the only thing different between michaels and my coach that i can tell. so it must be that. i can plug into any gfi circuit just fine.



James Tuckness
01-14-2009, 12:44 PM
I can probably explain GFI problems and how to "correct." You may or may not want to correct the problelm.

Too much to write here will be happy to answer questions in phone call. 417-866-0261

71-30' 391 gas

James Tuckness