Left Side Boat Trailer Tail Light Does Not Have Power when Bulb is Installed

Updated 05/17/2013 | Published 05/16/2013

Question:

I have a boat trailer for a 16foot aluminum boat. The brackets for the taillights and fixtures were replaced. Light bulbs, voltage and ground appears OK except that the driver side taillight on the trailer does not work. The current is nil with the bulb in place and when the bulb is not installed the voltage is good. The bulbs are good, any suggestions?

asked by: John B

Helpful Expert Reply:

The most likely problem is going to be a bad ground. Without the bulb in, there is no draw on that light and ground issues normally show up when there is a load on the system. If you recently install a plastic license plate holder in between the light housing and the trailer frame, that can cause this problem (if the lights ground through the mounting studs).

The solution will be to run jumper grounds (no matter how the lights ground to the frame) to the main trailer connector ground. This is a common issue on aluminum trailers because aluminum is not the greatest metal to complete a circuit.

expert reply by: Michael H