Troubleshooting Trailer Brake Circuit Activating When Turn Signal is Engaged

Question:

I purchased a 2010 f350 and hooked up to travel trailer, now the trailer brakes activate when left signal on with controller set at 4 and above. The trailer did not do this with my 2015 ram. Any ideas what issue may be? Thanks for your help

asked by: Kelly

Expert Reply:

If activating one function on your 7-way trailer connector causes another circuit to activate this usually means there is a corrosion problem in the truck 7-way socket. Since the issue did not occur with the other truck this suggests the problem is on the F-350 rather than on the trailer.

Corrosion in vehicle or trailer wiring can occur inside the connectors, where it is very hard to spot, as water slowly migrates inside them and becomes trapped. This can lead to corrosion that can cause to separate circuits to become bridged together, so when you activate the turn signal that power bleeds over to the brake circuit.

You can replace your 7-way socket with part # HM40975 that connects to the U.S. Car connector on the truck's wiring harness.

expert reply by: Adam R