In GMC built interior coaches. Are they house 12V body ground?

[Bob Dunahugh]

We've owned 3 GMC's. All 3 GMC's were 78 Coachman built Royales. Coachman installed ground wires to all appliances, and lights. All the ground wires went back to a ground bus bar that was next to the 12V fuse block. I see no ground bus bar. Both the 12V buzz box wires weren't attached to anything. So I assume that the buzz box neg. wire is to be attached to the coach body. I want to get the modern solid state 120V to 12V convertor installed to test the 12V systems. I'm painting all the backsides of everything that goes back in. ( For future odder, and moisture absorption control. ) This electrical work will give the items that I painted today. More time to dry before the installation. Bob Dunahugh The Building of a GMC.

 

[Ken B]

The aluminum body is the master ground for everything 12 VDC inside the coach.

On a Gm fitted 26 ft coach the converter is grounded to a body with a bolt behind the wall behind the converter.

The engine master ground is for everything powered by the alternator and secondarily serviced engine battery. Basically that is everything electrical
form the interior step forward and all outside lighting. The engine master ground is NOT directly connected to the body.

All of this is shown on the GMC wiring diagram and is downloadable from bdub.net if you do not already have it. I can also send it to you
electronically if you tell me what year coach you are dealing with. Ken H's son also has very large paper diagrams available.

Ken B.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[johnny]

Both grounds must be connected for the batteries to charge. The alternator is grounded to the engine. If it is not also grounded to the coach body,
the house batteries will never charge from the alternator.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[Ken B]

The ground path that Johnny is talking about is accomplished by 2 (and usually 3) braided jumpers. One is on the transmission to the steel frame and
the other one (or 2) are located across the body mount above the front right wheel and, if you have an Onan, is in the drivers side rear in the Onan
cabinet floor.

These are also the ground path for the boost operation. Do not run other ground jumpers because in a boost operation if the main jumpers are bad,
the high current will go through the added jumper and usually smoke it.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana