Vehicle Blows Fuse When Trailer is Attached

Question:

I have 1993 GMC 3500 that i picked up used about a year ago, the truck has aftermarket trailer plug in on it. When i plug my trailer into it it blow the fuse in the truck. I can plug this same trailer into my 2006 2500 with no issues lights work fine and no fuses blown. So this leads me to believe that the problem is with the truck and I have chased wires cleaned the connectors checked ground and nothing. Any ideas ?

asked by: Ernie A

Expert Reply:

I would agree that the problem appears to be on the vehicle side. Generally speaking, most of the time when a vehicle's fuse blows as a result from attaching a trailer, the cause is usually attributed to either the trailers lights exceeding the vehicle's trailer lighting circuit or there is a short somewhere along the wiring harness. If you have previously pulled the trailer with the vehicle in the past, then I would lean towards a wiring issue but if you have never pulled this trailer before with the vehicle then my assumption is that the vehicles trailer wiring circuit is not capable of handling the amperage of the trailer's lights.

If you have pulled this trailer with your truck in the past, then I would re-check the wires with a circuit tester like part # PTW2993. In order to do this, you will need to activate the vehicle's lights while testing the corresponding wires just before the vehicles trailer connector (with trailer unhooked). If one of the wires does not illuminate the test light and it should, I would trace that wire as far back as possible paying close attention for breaks or frays. Use electrical tape to close any potential weak or loose connections on the wire.

If you have not attached the truck and trailer together before then one could only be led to believe that the trailer's lighting circuit is exceeding the vehicle's trailer lighting circuits capacity. In order to fix this, I recommend installed the Upgraded Heavy Duty ModuLite Circuit Protected Vehicle Wiring Harness with 4 Pole Trailer Connector part # C59496. The powered coverter box included in this kit will draw its power from the vehicle's battery and distribute the correct amount to each lighting circuit on the trailer. If you have a 7-way trailer connector at the rear of the vehicle you could then use the Adapter 4-Pole to 7-Pole and 4-Pole part # 37185.

Let me know if either of these options provide a solution for you.

expert reply by: Conner L