Troubleshooting Blown Headlamp and Tail Light Bulbs on 2002 Toyota Tacoma After Harness Install

Question:

2000 Tacoma standard trans 2wd ext cab. Installed curt c55379 wire harness. NO LED on truck or trailer. Well grounded. Since install LEFT headlight and tail light burn out shortly after replacement. Connections look good. Nothing loose. Lights on trailer work well. Left brake light works well. Do I return c55379 for refund and call Toyota for what is the same harness? How di I fix this?

asked by: James P

Expert Reply:

Since the truck is 17-years-old my first suspicion is that the bulb sockets/connectors for the left headlamp and/or left taillight could have corrosion that is causing a dead short that takes out the bulbs. There could also be worn insulation for that circuit's wiring that makes intermittent contact with a metal structure due to vibration when driving the truck. This would explain why the bulbs may work when the vehicle is still but fail when you drive.

Normally the fuse for the headlamp/running light circuit would blow if the issue was that the trailer's total running light power draw was more than the 5-amp capacity of Curt harness # C55379.

I also suggest checking to ensure the correct value fuse is installed in the power box location for the running light circuit.

I would try driving the truck without the trailer, after you install new bulbs, to see if the malfunction occurs again. If not then this tends to suggest there is an issue on the trailer side. In this case inspect the trailer wiring for that circuit looking for worn or cracked insulation or any part of the wiring that may touch the trailer frame or suspension, causing a dead short.

expert reply by: Adam R