Tow Bar Wiring Causes Lights Not to Work on 1992 Elite Motorhome and 1997 Jeep Grand Cherokee

Question:

I have taken my motorhome to expert trailer wiringinch place and they cant seem to get my 1992 Desiel pusher Class A motor home Gilig chassis wired to a 1997 Jeep Grand Cherokee. The brake lights on the jeep quit working, so they tried another converter on the coach and it keeps blowing out. They ran all new wire to the back of the Jeep, added diodes and a new converter and now I dont have a right turn/brake on the Jeep and also the coach now. I am at my wits end and the experts have just thrown up there hands and told me sorry we dont know what else to do. Can you help me with some sort of diagram. The coach is pre electronic and the jeep has a brain/ electronic system. So does that make a difference?

asked by: Jeff O

Expert Reply:

You are just going to need the proper wiring kit. It sounds like there are a combination of problems that are leading to the failures. There could be short and ground issues causing the lights not to work and the converter to blow.

First, lets look at what is going on with the motor home. If it has a trailer connector on it you will want to test it using a circuit tester such as # PTW2991. I have included a link to a help article that explains how to test it. If some of the circuits are not working then you know that the issue is on the motor home side. If they all check out fine then the issue is likely in either the kit used or the Jeep wiring.

Since the diode kit is not working I recommend a different approach that will bypass the Jeep wiring all together. You could use a bulb and socket kit # RM-155 or you could use a magnetic kit such as # RM-2120. With either of these kits you will not have to splice into the Jeep wiring at all.

The bulb and socket kit is a more permanent solution for frequent flat towing. The magnetic kit would be good if you do not plan on flat towing the Jeep very often.

One issue that might be the cause of all of this is the diodes. On your Jeep you should be using a 6 diode kit, # 154-792-118158, if diodes are used at all. I have included a picture that shows how this kit should be wired up should you decide to go with the diode kit again.

Another possible cause could be incompatibility with a supplemental braking system if you are using one (most states now require it). Many of the flat towing converter boxes are not rated for very much power draw. If there is a short somewhere then that could be why it is blowing.

Going with a kit that bypasses the vehicle wiring should solve the problem unless the issue is on the motor home. If that is where the problem is then until that gets fixed you will likely keep having these problems.