Wiring Problems on a Vintage Chevy Motorhome

[jessey]

Hello Everyone,

This is my first post here and I'm hoping I'm posting this in the rigt place. I'll post some pictures of my moterhome later, it's in really good shape for being 39 years old and having 242000 Kilometers on it.


Is there anyone here that is familiar with the wiring of a 1981 Chevy Van 30 series. It is an 18 foot Frontier Motorhome. I just bought it a few days ago.

The problem is: with the headlights off then everything works on the rear. When I say everything I’m talking about the right and left turn signals, brake lights, running lights, license plate light and reverse lights. And with the headlights on then nothing works or very dim and hard to see on some bulbs especially with the Lenze covers on.

The first thing I did was to check and clean the ground cable at the battery post and also the ground strap where it attaches to the engine and the frame.

I had a piece of wire that is about 25 feet in length with attached alligator clips on both ends. I plugged one end of the wire into the start battery’s negative post and the other end to a white wire that supplies the ground to the rear lights. After supplying the ground then all the lights work as as expected, nice and bright with the headlights on. So it's definitely a faulty ground issue. All the wiring for the rear lights is coming from inside the wooden walls. There is no way that I can think of to do a good job of Mickey Mousing an extra ground wire into the back wall of the motorhome and I’d prefer not to do that. I’d like to find the problem and I’m thinking the problem is not in the walls (the motorhome has never had a water leak).

I’m trying to locate the point where the wiring for the tail lights is coming out from the Motorhome’s wooden walls and into the steel cab to the fuse box? Would anyone here have any experience with bad grounds in a Chevy motorhome? I'm thinking there would be a plug between the cab and the motorhome and possibly its corroded?

I’ll continue trying to find this plug but if anyone here has any suggestions to offer about the location of this plug or anything else then it would be greatly appreciated.


Thank You
jessey

[richard5933]

This is a very common problem, and it's good you at least know what you're looking for. I don't have specific advice for you on this chassis, but if it were mine I'd be starting at the headlights and working backwards. My plan would be to follow every wire in the headlight circuit, looking for any ground wires. There will probably be more than one.

If you can access the back side of the headlight switch, you might also find the ground wire connecting to the plug at the back of the switch. You can also work out from the fuse block looking for ground wires.

I've wrestled with this in many vehicles over the years, and I'd put money that your problem will be found at the front end of the coach. Probably near the headlight switch, fuse block, or the headlights themselves.

If the ground that serves the lights is weak, it might work fine with the headlights off. Once you turn on the headlights it suddenly can't carry the required current to provide adequate ground to all the lights, so the ones closer and with heavier gauge wiring get the current and the ones in the rear with the smaller gauge wiring lose out.

[jessey]

Thanks Richard,
The headlights were not working when I first got the motorhome last week. I did replace the hi/low beam switch on the floor and the headlight switch in the dash and the headlights work good now. I’ll check the ground on the headlight switch and poke around and see what I can find.
Thanks Again
jessey

[richard5933]

In my experience working on two older bus conversions, 90% or more of electrical problems like this can be traced to a bad ground connection - either a weak/bad connection or a rotted ground wire.

[Soppy]

On my 77 chevy motorhome there is a ground buss bar near the converter. That buss bar is also grounded to the frame. The wire from the tail lights may just connect to a spot on the chassis. The AC grounds are separate.

[Tidy Tabby]

On my G30 based Transtar, the main harness both for the house and the van itself is in the tower behind the driver’s chair. I created and color coded a wiring harness off of a hand-drawn one I found in some manuals I got in my 2nd rig. Look for it in the Transtar by Champion thread.
In my case, something was living behind the shower and chewed through the harness and killed my taillights, but I was able to fish some new wires from the plug in the tower behind the captains chair back to the taillights.

[garry1p]

You do not have to fish a new wire.
You said you ran a wire from the battery to to a white ground wire and all worked.



You can run a wire from frame ground to the white wire and that is the same as running a wire from the battery since the battery is tied to the frame ground.

[jessey]

Thanks for the advice guys.
I’ll be working on it next week sometime and I will post if I find something that’ll fix it.
jessey

[jessey]

Originally Posted by Tidy Tabby

On my G30 based Transtar, the main harness both for the house and the van itself is in the tower behind the driver’s chair. I created and color coded a wiring harness off of a hand-drawn one I found in some manuals I got in my 2nd rig. Look for it in the Transtar by Champion thread.
In my case, something was living behind the shower and chewed through the harness and killed my taillights, but I was able to fish some new wires from the plug in the tower behind the captains chair back to the taillights.

Hi Tidy Tabby,
Thanks for replying to my post, I really appreciate it. I found the post you were talking about for the wiring diagram but your link to it is no longer working. I copped and pasted your post below. Is there any chance you could repost it here.
Thanks
jessey

Originally Posted by Tidy Tabby

Scouring the internet got me a complete manual for both the GM van portion of this thing (which was easy, in fact I have three different manuals for the van) as well as a complete manual from the RV manufacturer. Unfortunately, as many of you have probably discovered before with these old van-based rigs, the wiring diagrams from the GM manuals only cover the van and thus are not relevant once you get behind the front seats. And the wiring diagram in the RV manual is terrible. It is complete, but it is at best a scan of a hand drawn wiring map, black and white and barely legible. So, in the interest in not losing my mind while trying to sort this thing out, I spent the last week asking around, squinting really hard, and color coded the wiring diagram myself. There are still a few areas where I could not clearly decipher what color some wires are (denoted by the green text boxes) and once I locate each of the individual plugs and connection points within the RV itself I will notate them accordingly for future reference but for the most part this tool will make life so much easier. Once I have verified all of my notes and located everything, I will be happy to post up a complete .pdf format copy of this for anyone else working on a Transtar.
Upon this rock I shall build my church...

[Tidy Tabby]

Sorry, the Photobucket apocalypse rears it’s ugly head again, I’ll have to get into my laptop and find the file again.

[leadman]

Not having a similar motorhome handy to look at what I can tell you is most likely the wiring for the tailights, etc is factory and running in the frame rail to the rear. I had a '77 GMC van and this is the way it was. So look under the rear of the coach at the rear. If it has a trailer hitch it probably has some wiring there for a trailer also.
If no luck there running a new wire might be the easiest fix. I would test the positive wires at the lights with a meter just to make sure corrosion has not reduced the voltage too much going to the rear. If it has you might want to trace this out to prevent future problems. Start with the fuse box under the dash and check the voltage and compare it to what is at the rear.
Worst case, since you have already replaced the switches you know where the wires start from and could run new back from there.

[billyt7563]

For what it`s worth, I have an 83 Pace Arrow w/ the P30 Chev chassis. I too had headlight/ turn signal wiring issues, and I found the ground bar behind the power center/ invertor, I could access it through the closet behind the power center. Once I cleaned the bar & terminals that solved most of my issues. Don`t know how yours is layed out, but that's how mine was..

[EyezOpen]

Perhaps you might take the approach of restoring the light system rather that repairing it. To me that means taking apart all four corners of the lighting and cleaning the entire assy...Grounds....power leads....and of course the housing assemble itself. From there it is all good news...simply use a voltage meter or light and check each circuit for continuity....if you had a power line shorting it would become apparent quite quickly....you have a bad ground and checking each corner for continuity will not only give you peace of mind for the future it will also help you find the ground with little guess work.

[Tidy Tabby]

I agree, there's nothing I hate more than not having or being on the road with other vehicles that don't have a full complement of working lights. Running lights, brake lights, head lights, headache lights, all of them should be working.