Trailer Keeps Blowing Vehicle Running Light Fuse or Trailer Running Lights

Updated 09/29/2015 | Published 09/28/2015

Products Featured in This Question

Standard Trailer Light Kit with 25' Wire Harness

(457)

$29.41

Hook Probe Circuit Tester

(70)

$12.41

Question:

I keep blowing the running lights on my trailer when I get my vehicle gas and start to accelerate the brake lights work turn signals work its just the running lights that keeps blowing

asked by: Donna

Expert Reply:

The problem you are having with the running lights on the trailer sounds like a short circuit somewhere. To find it the first step is to disconnect the trailer from the tow vehicle. Then use a circuit tester such as # PTW2993 to test the vehicle side connector while someone sits in the vehicle and goes through the light functions.

If the running light fuse blows while testing the vehicle side connector, then that indicates the short is on the vehicle somewhere. Check the connections for the wiring harness and make sure the connector is clean and free of corrosion.

If the vehicle tests out fine, then the issue must be on the trailer. Start by making sure the trailer side connector is clean and free of corrosion as well. Inspect the wiring going to the running lights and fix any pinched or damaged wires. Make sure the light grounds are all attached to clean bare metal surfaces.

If you continue to have problems, then it is possible that the trailer running lights draw more power than the vehicle side system can handle. To test that you could disconnect some of the running lights and if everything starts working then you know that was the issue. The solution is to switch to LED lights which draw a fraction of the power of incandescent lights.

expert reply by: Michael H