Troubleshooting Coach to Tow Dolly and Accessory Light Failure

Question:

Hello and thanks for having a way to ask questions! Application is a 1999 Safari Continental motor coach with amber turn signals 12V automotive I have replaced the vehicle incandescent light bulbs with plug and play LED. I have a 6 wire tow plug. I am connecting a 4 wire tow dolly with LED lights, and a basket with incandescent light kit above the dolly. I have a 6 to 4 wire flat adapter, with a split connector to light both. I had to have an RV shop put in a 3 wire to 2 wire connector to get anything to work and it all worked for awhile, but no longer. At one point, I could run the basket lights or the tow dolly lights not both together, and now I can do neither. Help! What do I need to get my gaggle to light again, and to not burn out?

asked by: Robert

Expert Reply:

Since the wiring system worked at one time, that would lead me to believe that there is a grounding issue. Ground issues are the most common wiring issues, and can present as partial or total signal loss. The best way way to troubleshoot a multiple stage system like this, is to isolate and test individual components of the system one at a time.

You will need to inspect and test each stage to find the problem. Visually, you will be looking for any loose or damaged wires, connectors, or noticeable signs of corrosion. If you see damaged or loose connection that will need to be restored. Typically corrosion occurs on the adapters or connection points. You will need to clean these locations with a brush removing any corrosion and I recommend using dielectric grease to prevent future corrosion.

For testing the system, I recommend starting at the 6-way on your coach, using a circuit tester like the PT tester # PTW2993. You will want to use the tester on on the function when activated and check for signal at that location. If the ground on the 6-way is not secure you may partial or complete loss of functions.

If you see no problems at that 6-way and all the functions are working properly then move to the next component in the system. The 4-way on the tow dolly check in the same way to see if the functions if those connections are working. If they are, then move onto the basket wiring connection and see if that connection is receiving the proper signal.

If you do not detect an issue using the circuit tester, and all the functions of your wiring system provide the correct signal, then it is time to check the wiring itself. You will want to look for loose connections or damage to the wiring, a loose ground on any of the connectors, or a light. Keep in mind some of the lights ground through the mounting hardware, and some have a ground wire on the light itself.

I have included a couple of our help articles, diagrams, and a quick testing video to help you out. If you are still having trouble after completing these step please let me know and we can explore other options. But typically trailer light (tow dolly in your case) are caused by an bad ground.

expert reply by: Rachael H