open (Electrical) ground (Electrical Question)


Old 10-15-06, 10:22 AM
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Join Date: Nov 2005
Posts: 56
Angry open (Electrical) ground (Electrical Question)

We just bought a used 1996 Motor home. Power 110ac from garage to 50 amp cord on RV.
It has a generator which we havn't turned on yet.
a 50 amp power panel with a converter for the house batteries.
It has about 9 -110ac outlets one for the Microwave and one for roof AC which is also ac power. I did a Polarity test on all the outlets.
it should open ground. At the power/convert panel I found if I turned off the Air cond. breaker the tester went to normal on all outlets.
So I took the cover off looked at the air's wire all looked good.
I then removed the breaker for the air cond and looked at it all looked okay. I then pulled the rest of the breakers out make sure all wires where tight. Put all back togeather. I then fliped each breaker on and off a few times. Still test shows bad. I turn the breaker for microwave off the tester shows normal. I un plug the microwave from the outlet. All is normal. I plug the microwave back in and heat some water again all is normal.
Can a breaker that hasn't been used in 10 years say and was in a damp environmental (looks the other owners didn't air and heat the rv very well in the winter) cause a problem or is this a swinger that over time the problem will happen again?
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Old 10-15-06, 09:08 PM
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Join Date: Nov 2005
Posts: 56
follow up more in fo.

Follow up to my original post.
The power to the RV is 50 amps it then goes to a breaker box in the RV.
Which has 2- 50 amps. (Main) breakers here are the rest 1- 30 amps. and 1- 20 amp.
Then some how it gets to the convert box, which has 110vac on one side with breakers. 110vac as follows breakers 1- 30amp main, 1- 15amp Microwave 1-15 amp for the GFI 1- 20 amps Air conditioning 1-15 amp for outlets and 1-15 amps for the converter box
side just has DC fuse.
This morning after see what the microwave did to the tester I unplugged it.
I left the tester plugged in all day while running shop vacuum and doing some jig saw cuts and drilling. All went normal. I plugged in a space heater setting it at 700 watts after a while I looked at the tester sure enough show open ground. So I unplugged it and back to normal the tester went.
Then I plug the micro plug back in to the outlet the clock came on and the tester went to open ground. Unplug the microwave all back to normal.
I would hate to tell my wife she can't blow dry her hair on one of our trips.
Old 10-17-06, 07:35 AM
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Join Date: Nov 2005
Posts: 56
Yesterday all day had no problem with all power units running.

the only thing I did do was tighted up on the shore power plug (plastic ring) that secures the plug to the RV.
Old 10-22-06, 06:30 AM
Join Date: Jan 2006
Location: Ontario, Canada
Posts: 759
One thing we always do Jeff, when we show a problem with polarity inside the motorhome, especially in multiple places, is to check our receptacle that is supplying the power, as well as any extensions we used to get power to the unit. Quite often it was our supply that was causing us to think it was inside the unit somewhere. Try another receptacle, with a good extension cord if necessary, and see what happens. Another area was in that automatic switchover box where the generator & shore power are fed into. With unit unplugged, generator off, open the cover and you will see what looks like contact points in there. I use a nail file, but you can use what is available to you, like emery cloth or sandpaper, and clean all those contact surfaces good, and see if that helps at all. While your in there, check all connection are tight also. Let us know.
Old 10-22-06, 08:39 AM
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I'm not familiar with the finer points of RVs'.

From an electrical stand point it sounds like a connection issue.

That said, it very well could be the main point of attachment,or all the way to the receptacles.
If the moisture was extreme, its possible that there is some oxidation in these connections.With the loads these connections could be loose as the ckt heats up causing an open,then as the ckt cools reconnecting.

I would start at the main shore connection and go from there, things due wear out.

Good luck.
Old 10-24-06, 07:34 AM
Thread Starter
Join Date: Nov 2005
Posts: 56
Thanks for the replys,
The problem was is in the 50 amp. Plug from the garage to the RV.
The ground wasn't contacting all the the time.
Thanks again,


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