Troubleshooting Trailer Running Lamps that Flicker When Parked

Question:

I have a Audi Q7 with the factory tow package towing a trailer with LED lights. When I park with the trailer connected, the tail and clearance lights have a faint flicker going on. When I turn the lights on it goes away. Will the bulb out bypass adapter solve this? I havent really had a problem with vehicle telling me that theres a bulb out.

asked by: Craig B

Helpful Expert Reply:

All the # C35FR adapter does is add a little bit of a load to the lighting circuits to prevent the bulb-out light or warning from going off, it won't solve the issue you describe.

What could be happening is that the trailer connector on the vehicle or on the trailer has some corrosion built up on the pins/sockets that power the 12-v circuit and the running lamp circuit which would make sense as the pins are adjacent in the trailer connector. At a certain point once the corrosion gets severe enough, it can migrate to the interior of the connector and 'bridge' the two circuits slightly which would provide a small amount of constant power to that running lamp circuit on the trailer.

If the connectors on the vehicle are of the type that can be disassembled so you can check the individual circuits connection to the terminals for the pins, you can pretty easily confirm that this happened.

You can replace the 7-way on the vehicle using a replacement connector like # A10-7072VP and the connector on the trailer using part # 277-000141 which includes a junction box so your connections will be squared away and protected from the elements. For the 7-way on the trailer side, be sure to pay attention to the wire color codes listed on the product page for the # 277-000141, as they might be different from what's on your trailer.