Trailer Clearance/Marker Lights Do Not Light Up But All Other Lights Work

Updated 05/19/2015 | Published 05/17/2015

Question:

2006 haulmark enclosed trailer the upper lights front and back and lic light turns, and brake all work the lower reds and fender lights no go, even changed the two prongs lights/bulbs, check the ground I am getting 12.4 at the pickup end but less in trailer from 6.97 to 11.5, seems to get higher when pickup is running but under 12v, where does the problem lay???

asked by: Michael

Expert Reply:

It sounds like there is some issue in the wiring or possibly a new ground location is needed for the affected lights. Inspect the wiring from the front to the back and look for any pinched or frayed wires and repair as needed.

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.

It is also possible that there are more lights than the vehicle tow package wiring can handle. The way to test this is to disconnect other lights on the same circuit. If the affected lights start working like normal then you know that they are drawing too much power. The way to fix this would be to switch to LED lights which have a fraction of the amperage draw of incandescent lights.

expert reply by: Michael H