| [GMCnet] Found my electrical gremlin [message #303624] |
Fri, 15 July 2016 09:54  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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As I posted earlier, a few weeks into this Alaska trip we started have an issue with the chassis battery unexpectedly running down over night while dry camping. Never happened before. We also had strange behavior with some of the house 12vdc appliances and there also was a 12.x voltage showing between the chassis negative cable and negative post. I could not find an explanation for all of these symptoms so did a quick rewiring of a couple of the appliances to provide known 12vdc from the house battery and good grounds for each. We also stopped dry camping and as long as we were plugged into shore power never had the chassis battery run down again. But I never could find any root cause for these strange behaviors.
Today I took everything out of the coach to do a deep cleaning. In the rear, under a platform beneath the center section of the rear U shaped lounge I found four ground wires had come loose from a master ground back to the aluminum body structure. Apparently without those grounds the circuits they were supposed to ground found an alternate path to ground that somehow involved the negative on the chassis battery. While I can’t explain the why, fixing those grounds did appear to eliminate the 12.x volt drain between the chassis battery and the chassis negative cable (measured drain now is 0.16vdc) and the temporarily rewired appliances now work properly again with the original wiring. Strange. Never take anything for granted when it comes to grounds I guess is the lesson.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] Found my electrical gremlin [message #303628 is a reply to message #303624] |
Fri, 15 July 2016 11:25  |
Handyman
Messages: 229
Registered: April 2016
Location: The Netherlands
Karma: 2
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Senior Member |
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Hi Jerry,
Electricity is like water, it tries always to find a way ....
I had a Satelite receiver which had no on/off switch. So I thought, adding one would stop the 12volt from slowly running down the battery, in rest.
I did all the things needed... Put the switch in the negative line.
Testing it, only with the sat recever connected to the12v, it worked fine.
After mounting it and connecting HDMI and the satkabel, the switch seemed to misfunction, both switchpositions, did switch the sat receiver to ON !!
At first I thought the switch got stuck somehow, but as I tested it again and again, Standalone it worked. All connected it did'nt 
Pffff ... What the H....! But then I found that it got its negative connection also through the satkabel.
Rewirering the switch to the positive cable, did the trick.
Daniel
Daniel Jacobs, NL-USA 1977 GMC Eleganza II, Rebuild 455 (2019) 3.55 FD. FiTech and (Modified) FCC, Electric Pump, insulated GasTanks, 100A Alternator, APC, McDash, Schräder Valves + extern Fills, Ceramic Film, TPMS, FlexSteel Seats
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| Re: [GMCnet] Found my electrical gremlin [message #303631 is a reply to message #303628] |
Fri, 15 July 2016 13:38 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Both of these are good examples of why I tell people NOT to run parallel wires back to the master ground. When the main (intended) ground path fails you get some strange and hard to diagnose problems.
I'm happy to see that you found the issue.
I have had to chase a couple of those PO installed issues on my coach. In one case a PO ran a ground wire between the passenger seat overhead light to the overhead light above the dinette. The dinette light gets it's ground from the aluminum body while the passenger seat is suppose to ground to the engine. I only found the problem after the wire smoked behind the plastic wall one day when I tried using the boost switch to start the Onan.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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