I have an electrical problem with the chassis lighting components on our 92 Breakaway. The "Right turn signal" functions OK until I turn the headlights "ON". When headlights are ON the right turn signal "indicator" dims at the dash and stops flashing. Looking at the back of the coach the rear backup lights mounted on the bumper are dimly lit. This symptom occurs with the engine running or not. I did recently "clean up" my trailer wiring harness and could have possibly wired something wrong and maybe even damaged some component. Today I removed all the wiring from the factory harness to the male hitch trailer connector in an attempt to isolate the problem.no change in symptom. Another weird malady is while testing the output for the trailer wiring I came across a ground wire that was "live" (lit my test light) soo I'm guessing I have a short somewhere. But what circuit do you think it relates too? The wiring diagrams are not very clear. Why do the two "clear fog lights" turn ON (mounted on rear bumper) have to do with my right turn signal malfunctioning only when the headlights are turned on?

Does anyone have a electro mechanical schematic for the driver side outside electrical compartment? Something that tells me what some of the relays tie to?
Coincidently my cruise control quit functioning the same time my lights started acting up.

I would suspect a bad ground in the parking lights, which come on with the headlights - I don't think the headlights are the culprit (try it with just the parking lights on and see if the symptoms are the same). If they are, remove the parking light bulbs and see if the issue persists (with the parking lights on).

The rear-mounted lights on my '94 Breakaway are docking lights (and are in addition to the backup lights in the cluster), and are controlled by a separate switch on the dash (but mine has the GM instrumentation because it has a GM 6.5L TD...)

You didn't say if the trailer harness wiring is live with the ignition turned off, nor the number of connectors, but some connectors are wired to allow the engine alternator to charge a travel trailer's batteries - and some aftermarket hitches come with that type of connector standard assuming the provision is needed, so the live wire wouldn't be abnormal - you just wouldn't use it for a Toad or utility trailer.

The cruise control could have stopped functioning due to electrical or mechanical issues....It could be something as simple as a blown fuse.

The problem is a bad ground - the rear tail light is searching for a ground and is finding it thru the turn signal light circuit.

That live wire for the ground that you mentioned is the ground wire trying to find it's ground - you're going to think I'm off the mark here but I would just take a temporary jumper wire and touch the "hot ground" and have the other end hooked to something like the rear ladder to see what happens. Trace your ground circuit down.

Keep this in mind - If in fact the ground wire was "hot" and it was already on a good ground it would have popped the fuse!

See, bad ground. I know, everything is telling you not to touch that "hot ground" to a real good ground. Go ahead, do it. The worst that could happen is you will need to replace a fuse.

I have had a bad turn signal switch do about the same thing.

Hi Bill and Rusty, thank-you both for your quick replies!!! Taking Bill's advice, I took a jumper from Ground to the chassis wire loom ground (white)and "Presto"! problem solved. I started to explain to my wife how we solved the problem but realized I still don't understand myself. Why run a ground wire through a wire loom when you can access a ground anywhere along the chassis? Where does the other end of this ground wire go? Thanks again guys.

The other end of the wire should go to a good ground. If you don't trace it back don't sweat it. Just run another ground wire of sufficient size and properly attach it.

The reason behind how it works is simple. Example: Take a headlight. There are usually three wires running to that. 1 high beam - 1 low beam - 1 ground wire. If you had the ground wire off of that one the headlight would be dim and the other headlight would have the high beams on (dim) at the same time as the low beam. The electrical current is trying to find a ground and now it's using the other circuit to backfeed thus giving it a "hot" ground.

I noticed a lot of dim lights on my Barth when I got it. All was traced to poor grounds. It seems that Barth liked to use a "bus bar" type of ground. They then linked all of the wires up to that bar and then ran it to another good ground.

On my 91 the ground wires were, for the most part, all green. On most trucks the ground wires is the white wire. On the battery the ground is black. Anyone confused yet? You would think they (whoever they are) would stick with one color.

If you go the route of running a new ground wire, and there is more than one thing hooked to it, use an 8 to 10 guage wire. Ground out both ends of the wire. Try to trace it out.

The best trouble shooting tool is a full length wire with an alligator clip on each end. You can use it to provide a battery ground or a battery positive to every device on the vehicle. It can also get you home if things are really bad.

Much better than removing a convenient length from a nearby electric fence and irritating the farmer. I did that once when I was with someone else, and left a ten dollar bill taped to the cut end of the wire.

Great advice! Indeed, a long jumper cable can save a lot of time tracking down faults in both hot and ground. I have two (and need to make two new ones due to the length of StaRV II) - because sometimes both need to be checked at the same time.

I would never go anywhere without a test light. The jumper wires are good too. You should also learn how to jump out a defective relay and know how to test one to see if it's working.

Instead of just leaving you with a "jump out the relay" I thought I would post what I meant. This is a diagram that I made up to help explain it.



Regular relay: (SPST) Normally-open
A relay is used to get a high amp load to work with a low amp switch. It does this by pulling in a magnetic coil. The pins 85 & 86 is the electro magnetic coil wires. Pin 30 is the high amp feed wire. Pin 87 is what your trying to get the high amp feed too control. This is how a typical relay would work.

Change-over relay: (SPDT) same as above but...
Now pin 87a is just a crossover. If you wanted to go from low beams to high beams headlights then 87a is always hot until you operate the switch that makes 87 hot. Pin 87a breaks contact to get pin 87 hot.

To jump out a typical relay run a heavy guage wire between pin 30 and 87. If it was headlights then jump out 30 to 87a. This would get you low beams and allow you to continue.

Most people use a change-over 5 pole relay for a normal relay setup and don't hook up pin 87a.

This is enough info to get people in trouble. Ask away and I'll try to explain it better.

Edited to answer a private question. The person did not want to ask in a public forum. I told them to check back here so everyone could benifit:
How would you hook up a 1 wire horn
1) run a wire from 86 to 30
2) hook 30 to constant on - install a fuse
3) hook 87 to the horn
4) ground out the horn
5) hook 85 to the horn button

The horn switch is open - each time you hit the button it grounds out. When the low amp horn switch grounds out it pulls in the electro-magnetic coil and sends power from 30 to 87 thus beeping the horn.

Before you condem the relay:
1st find out if 85 or 86 is hot. Remember this info.
2nd take the test light and clip it to a hot source. Take the test light probe and touch a ground. test light should come on.
3rd touch the one wire at the relay post 85 or 86 that did not light up test light in 1st test and then hit the horn - test light should light if the horn button is working

Great post!