Brake Lights Blow when Testing Trailer Wiring Installation on a 2007 Lexus ES 350

Updated 07/02/2013 | Published 06/29/2013

Question:

I installed wiring and both elements on the cars brake light bulb blew before connecting to trailer. tail lights, turn signals elements are fine. Was it because ignition was off/on during installation to test ?

asked by: Jim S

Expert Reply:

When installing a powered wiring harness like # 118488 you will want to have the fuse out of the fuse holder (inserting it is the last step) and have the negative battery cable disconnected. Then you will make the connections at the tail lights, route and connect the power wire. Then reattach the negative battery cable. And finally insert the fuse.

Lights blowing (or fuses or the converter box) indicate a short circuit. This could be caused by a missed connection, bent or broken pin or power wire connection to the wrong power source. You will also need to make sure the converter ground wire is attached to a bare metal surface.

If the stop light fuse continues to blow when you try to install the harness then there could be a short inside the harness and it will have to be replaced since there are no user serviceable parts inside. I have included a link to an FAQ article that might also help.

expert reply by: Michael H