electrical short - Montana Owners Club

2bornot2b · 07-08-2009, 02:08 PM

When plugging into a 15amp outlet with a ground fault recepticle the breaker trips. This can be avoided if the living room and front bedroom AC 110v breakers are turned off. When I continuity test at the male end of the power plug on the trailer there is a 4 milliamp resistance. As far as I know this may have existed since the 2006 model 3760 was new as I just ran across ground faults in a county park in Big Eu Plaine, Wi. near Stevens Point, Wi.I have checked every connection I could find for a bad ground. Any help is appreciated short of tearing into the walls. In a non groung fault recepticle of 15 amps or larger this problem does not exist. The factory referred me to the dealer. At $110.00 per hour for we will look until we find I am not too exited.

Countryfolks · 07-08-2009, 02:49 PM

Have tried using one of those cheap circuit testers? They test for messed up wiring at the receptacle.

jwedell · 07-08-2009, 03:03 PM

The resistance at the trailer plug is probably normal (it is measuring the total resistance of all loads in the trailer). When you plug into a GFCI protected outlet does the circuit breaker trip or does the button on the outlet trip (big difference) Also has the outlet worked fine in the past or is this a sudden problem. It's unlikely that a ground problem will effect the circuit breaker tripping. There are others who are also electricians and between us I hope we can help you. But we may need more information. Also what are you plugging into the outlet.

ARJ · 07-08-2009, 03:50 PM

First, spend a couple of bucks and get one of these to test the gfci outlet itself. You can get one at Lowes, Home Depot, etc.

http://www.amazon.com/Gardner-GRT-50.../dp/B00004WLJV

Second, gfci outlets can deteriorate over time-it may be easier and cheaper to replace the one you have with a new one before you go pulling your hair out looking for a high resistance short.

Now, I don't understand your explanation of "4 milliamp resistance". Resistance is measured in ohms.

You should check for a high resistance short between the HOT leg of the trailer and NEUTRAL. If there is one, start popping breakers until you find the one that eliminates the short. You should use a high quality, digital, VOM as the elcheapo ones may not show the short if there is one.

Trailer Trash 2 · 07-08-2009, 04:02 PM

And this is the tester you use to test a GFI circuit the other tester is for a standard 2 wire and a ground.
http://www.amazon.com/Gardner-GFI-50..._ob_hi_title_0

Art-n-Marge · 07-08-2009, 06:57 PM

Hey ARJ.... thats el cheapo, not elcheapo.... I may not know how to speak Spanish, but I do know how to spell and read Spanish. Wierd, huh?

ARJ · 07-09-2009, 02:37 AM

Thanks for the corrections guys!

noneck · 07-09-2009, 02:03 PM

Interesting...so when I bought my used Monty I too had a GFCI trip issue as my home setup fed by 30 amp GFCI. After many days of debug I found the issue in my Dometic AC unit. I had it narrowed down to the unit and pulled the plastic cover off on top of roof. The wiring routed a bundle past the compressor housing and happened to rub through the neutral (white) wire so it was touching the metal casing. Used electrical tape to re-insulate and tie wrap to pull the bundle away from rubbing metal surface.

2bornot2b · 07-09-2009, 04:24 PM

Quote:

quote:Originally posted by jwedell

The resistance at the trailer plug is probably normal (it is measuring the total resistance of all loads in the trailer). When you plug into a GFCI protected outlet does the circuit breaker trip or does the button on the outlet trip (big difference) Also has the outlet worked fine in the past or is this a sudden problem. It's unlikely that a ground problem will effect the circuit breaker tripping. There are others who are also electricians and between us I hope we can help you. But we may need more information. Also what are you plugging into the outlet.

BB_TX · 07-10-2009, 05:06 AM

A GFCI outlet compares the current flowing thru the hot wire to the current flowing thru the neutral wire. The two must be almost exact (within 4-5 milliamps) or the GFCI will trip. An electric circuit must be a closed loop (i.e. what goes in must come out) to operate. When correct, all current flowing into the hot wire will flow back out the neutral wire. There will be no flow thru the ground wire (except maybe some induced current).
Could be a short between neutral and ground (allowing some current to leak out thru a ground path), likely. Or could be a high resistance short between hot and neutral or ground (a low resistance short would probably trip the breaker), not as likely.
As stated try to isolate it to one circuit. Then concentrate on troubleshooting that circuit and/or appliance. May well be something inside the associated appliance.

2bornot2b · 07-11-2009, 04:51 PM

I have plenty to go on regarding blowing GFI tripping. It is narrowed down to 2 circuits, front AC and living room. I will troubleshoot the AC first. Ir the issue is in the walls of the front room I will never get access and will have to live with it.

NCFischers · 07-12-2009, 02:20 AM

There is a 99% chance that your problem isn't "in the walls". Turn off the AC breaker and plug in your trailer. If the GFCI still trips, turn it back on and turn off the other breaker. If it trips, unplug everything on that circuit. If the breaker doesn't trip, something that was plugged in was the problem. Good luck.

noneck · 07-13-2009, 02:38 AM

Here's the pic of what I found when I took the cover off, up on roof, Dometic A/C Unit...look closely at the "white" Neutral wire!

This was intermittent failure...had all circuits off would typically trip when "damp" out (must have helped with conduction to metal surface).

Mr.oddjobs · 07-14-2009, 03:36 AM

Quote:

quote:Originally posted by 2bornot2b

When plugging into a 15amp outlet with a ground fault recepticle the breaker trips. This can be avoided if the living room and front bedroom AC 110v breakers are turned off. When I continuity test at the male end of the power plug on the trailer there is a 4 milliamp resistance. As far as I know this may have existed since the 2006 model 3760 was new as I just ran across ground faults in a county park in Big Eu Plaine, Wi. near Stevens Point, Wi.I have checked every connection I could find for a bad ground. Any help is appreciated short of tearing into the walls. In a non groung fault recepticle of 15 amps or larger this problem does not exist. The factory referred me to the dealer. At $110.00 per hour for we will look until we find I am not too exited.

Mr.oddjobs · 07-14-2009, 03:42 AM

If this has been a problem since you took ownership of the unit, the GFI recepticle could be wired wrong in the circuit. Some GFI recepticles will go bad and start leaking a small amount to ground when you plug a load into them. This type of problem will trip the circuit breaker and not trip the GFI. I would check the wiring of the GFI and/or replace it before going much further.

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