I recently purchased Thor Class C built on an E-350 chassis. When I turn the headlights to the parking light portion of the switch all the marker and parking lights work as they should but when I pull the switch to the headlight mode the head lights come on but all the running lights go off. I checked the towing connections for shorts and they all look good. A search of the net for a wiring diagram was an effort in futility. I sure could use some help with a source for a wiring diagram and information. Thanks in advance for feedback.

 

I'm betting its your switch if they work when in parking light mode. The power is there so likely that something in the switch is broke. What year is the chassis? Check rockauto or Napa for a good replacement.

 

It is 1997 chassis. I purchased a new replacement switch but it does the same thing that the old one did.

 

A couple of clarifications, please:

This is the behavior since you got it? It's never worked correctly since you have had it?

Also, how are the towing connections involved? Are you having this problem only when a trailer is connected? Or does this happen whether a trailer is connected or not?

 

Yes it has had the problem since I purchased the unit. As far as the towing connection , it was just an effort to find what I hoped might be an obvious problem. I have not hooked a trailer to the unit so it is a problem anytime I turn the lights on. I appreciate any help you can offer.

 

Okay, thanks for clearing that up. Now, let's see what we have:

1. Headlight switch in parking light position, all running lights work as they should.
2. Headlight switch in headlight position, headlight works as it should, parking lights go off.
3. New switch shows the same behavior.

Did I get that right?

This would be a lot easier with a wiring diagram, but like you, I have not had any success in running one down.

So, let's try some basic checks and see if we can sort this out.

Out near the battery on my 96 are some relays, mounted to the front of the engine compartment. I suspect one or more of them is part of the lighting system.

See if you have the same relays, and if you do, use a meter to see if you get voltage to any of them when you pull out the headlight switch. Try both positions. If you get any voltage that switches with the headlight switch, take note of where you get what, and report back here. We'll try to figure this out together.