Right Trailer Lights Dim and Blinker is Not Working on Trailer Towed by a 2008 Toyota Highlander

Question:

I purchased the 118449 wiring harness for my 08 highlander and when plugged in the right side tail light is brighter than the left and the turn signal does not work on the right side either. we tested the connections under the dash and found that the incoming green wire to the converter box works the turn signal and brake light as advertised, but the outgoing green wire from the box has a steady power pull. My question is why is there a 10 amp fuse both in the under hood fuse box and the wiring harness itself, if the converter burns out before the fuses do? I was told that we were pulling to many amps for the set of lights we have on the trailer so I bought LED lights to try and bring the amps down. But why would one side work properly and the other not? Thanks in advance.

asked by: Frank P

Expert Reply:

This sounds like it could be a combination of problems though I suspect it is all related to one issue. It sounds like there is a ground problem on the right side of the trailer. To run down the ground, start by checking the vehicle side and trailer side connectors for any dirt or corrosion and clean them out.

Next, make sure the main ground on the trailer from the trailer connector is attached to a clean and corrosion free bare metal surface. Then, do the same with the taillights. A lot of trailer lights ground through the mounting studs unless there is an obvious ground wire. In either case, make sure there is no corrosion.

A bad ground or short to ground could be causing the constant power draw on the green wire on the output side of the converter AND be causing the dim light and blinker not working. To eliminate the converter as the issue you can use a circuit tester like # PTW2993 if needed and check the green wire with no trailer connected. If it still shows a constant power draw, then there is something wrong in the converter and it will need to be replaced.

The factory tow package for your vehicle probably includes the 10-amp fuse but adding another fuse on top of that should not cause this issue.

expert reply by: Michael H