Troubleshooting Wiring Gremlins on a 1966 Roadrunner Travel Trailer

Question:

Just purchased 1966 Roadrunner travel trailer. The lighting is a mess. The trailer has 3 wires coming out of it, read, green, and brown. My truck has a 7 Blade connector so I bought the plug for it and 25 feet of new wires. In the new wire set there is white, brown, yellow and green. I put the the new wires where they should go in the new connector plug. But when I turn on the left blinker its ok, turn on right blinker and nothing, hazards on and the left will blink as well as the license plate white light.. and it does other weird things that I cant remember its all out of whack. I believe Ive got a good enough ground but could that be the culprit?

asked by: Kenny

Helpful Expert Reply:

A bad ground can cause all sorts of weird things to happen. You also have to be careful when wiring because there isn't really a standard wiring color/function code for trailers. If the 7-Way you bought had any wires attached to it then they won't necessarily match up to the white, brown, yellow, and green.

For example on a trailer side 7-Way a lot of times there will be a red wire for left turn and brake lights, brown for right turn and brake lights, and green for running lights. It sounds like you will need to switch the wires you have between the right turn/brake and running lights. The license plate lights runs off of the running light circuit so it blinking with the hazard lights makes me think they are just swapped.

I have included a picture that shows the common pin out of a trailer side 7-Way. the key is to wire it up by function and not by color.

Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light but can show up any time.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H