Original Battery Connections

[gdbeckst]

Hi all,

I am about to mount my body back on the frame and I'm reinstalling the 3 OEM grounding straps (frame to trans/engine, RF body mount, LR body mount).

Now I'm wondering: Where do the batteries connect to?

My understanding from what I recall:

The engine battery positive (+) goes directly to the starter and the "VEHICLE BATTERY POSITIVE" distribution block

The engine battery negative (-) goes where?

The house battery positive (+) goes to the "battery boost" relay and output diodes, and then to the house 12V fuse block in the closet via a red 10ga wire that runs along the DS of the vehicle.

The house battery negative (-) goes to the radiator frame bolt?

I have read all the "GMC MotorHome grounding" information, reviewed the wiring diagram. I am an electrical engineer, so I know what I'm doing.

If anyone could snap a couple pictures for me, that would be awesome!

 

[tmsnyder]

Hi George,

Mine's in the driveway, can you stop by for a beer and take a look?

Todd

 

[gdbeckst]

Hi George,

Mine's in the driveway, can you stop by for a beer and take a look?

Todd

I'll come by sometime. Got a lot going on this time of year!

 

[RF_Burns]

I would run the engine battery positive (+) directly to the starter, then a jumper from the starter to the Vehicle Battery Positive terminal. This reduces the wire length by several feet for the high current to the starter compared to the OEM wire routing.

The engine battery Negative goes directly to the engine block. There is also a smaller wire from the engine battery negative terminal to the aluminum plate under the passenger side hood. This wire provides a ground for the dash which is mounted on the SMC. The frame and body get their ground from the 3 OEM grounding straps you have already installed.

On my 1977, the batteries are in the rear and the house battery Negative terminal connects to the body framework. Since your house batteries are up front, I would connect the house battery negative to the engine block as well. This will reduce voltage drops across the 3 grounding straps when you need to use the Boost switch to start the engine. The current in and out of the house battery is normally much lower than when doing a boost crank so the voltage drop across the grounding straps is negligible.

 

[Don Jaksa]

Here is a document on grounding and the GMC by Ken Burton

Electrical grounding in the GMC Motorhome

The GMC has 3 electrical grounding systems. This document by Ken Burton explains each and how to ground additional equipment. Posted by permission from Ken Burton P. Eng

www.gmcmotorhome.org

 

[Ken B]

Here is a document on grounding and the GMC by Ken Burton

The story about that document is someone asked for a one time seminar at an Eastern states rally so I threw that document together. Since then that document has been copied, made prettier, and accidentally trimmed some off of the top. I think the original might still be at Eastern states. It makes no difference where you might find it since they all have info.

I do not know if I would trust the author tho.

 

[Seeburg220]

Many of the slides (pages) of this download are cut off : (

 

[Christo]

Many of the slides (pages) of this download are cut off : (

Fixed.

 

[Seeburg220]

Fixed.

Thanks Christo! That's a great read.

 

[Don Jaksa]

Thank you for straightening out the formatting on the document

We all benefit

 

[Christo]

Thank you for straightening out the formatting on the document

We all benefit

No worries, Bruce Hislop (AKA The Resource Meister) had already uploaded a clean version of the doc to the Resources area here on the forum. It takes a village!

 

[Ken B]

It is great it is fixed but the original bad one is still on the GMCMI site and also needs to be replaced too.

 

[RF_Burns]

I believe they are revamping the whole GMCMI website.

 

[Christo]

It is great it is fixed but the original bad one is still on the GMCMI site and also needs to be replaced too.

@werewilfs