Troubleshooting Trailer Brake Lights that Do Not Work When Parking Lights are Switched On
Updated 06/20/2012 | Published 06/18/2012
Question:
when using the HM47425 adapter, everything work properly but the brake lights. when the parking lights are on the brake lights will not work. Check all the wires with test light, check wires on trailer and tractor using diagrams on your web pages for references. tractor is a volvo single axle, trailer is a gooseneck thank you for your help.
asked by: Dmc
Expert Reply:
It sounds like you have a poor or insufficient ground connection. The dead giveaway is that everything works okay unless the parking lights are on. When the parking lights are on, you are drawing near the maximum amperage through the trailer wiring, which is when a ground problem will manifest itself.
Check the ground connections on both sides of the tractor/ gooseneck attachment. Make sure that the ground connection for the connector on the tractor and the trailer are secure and not corroded and that the connection point is not covered with excessive undercoating. Each of the trailer lamps typically pick up their ground connection by being in physical contact with the trailer frame. If the lamps are mounted to wood or plastic, make sure there is a separate ground jumper ran from the lamp to the trailer frame to complete the ground circuit.
