Troubleshooting No Brake Lights With European Trailer Connector Adapter on 2002 Volvo V70 XC

Question:

Hello! I recently purchased part 118710 for my 2002 Volvo xc70 which has the factory tow hitch wiring harness. When I connected the plug adapter into the 4 pin on my new trailer, I get functioning running lights and turn signals but no brake lights on the trailer. What would I need to be able to have brake lights working on the trailer?

asked by: Jerzy

Expert Reply:

We haven't run into this in the past with customers who have used the # 118710 so I would start by checking the vehicle side connector. The brake and turn signals are separate on your European style 7-way so you will need to determine which pin is the brake signal and check for power using a tester like the # PTW2993. It may be that there is some corrosion on the connector as well, especially since it is a 2002, so it would be a good idea to check it and clean as necessary.

If you don't have power on the pin, double check for power on the wire running into the 7-way. If it doesn't have power here it is likely a short somewhere. You will need to locate the short and repair as necessary. If you do have power running into the connector, check to make sure the wire isn't loose or disconnected. If the connector is damaged you will need to replace it entirely.

If you have power on the brake signal pin then I would check the 4-way end of the # 118710 for power with it plugged into the vehicle. If you don't have power here it must be a faulty adapter. Since your turn signals work I doubt it is an issue on the trailer side since that runs on the same wire as the brake signal. However, it never hurts to double check the ground connection just to be sure.

expert reply by: Robin H