Troubleshooting Trailer Brakes Not Working Towing With 2018 Ram 3500

Updated 10/16/2024 | Published 07/30/2019

Question:

2018 3500 RAM. Only 5 volts on trailer brakes with a gain of 10 on heavy electric. The brakes work fine when hooked to another truck.

asked by: Thomas

Expert Reply:

I am happy to help you troubleshoot your braking issue. Since the trailer brakes on the trailer work properly when hooked up to another truck then your most likely experiencing a wiring issue or defective brake controller on the truck side.

Most of the time there is an issue with the pins on the 7-way connector on the truck. You want to make sure the pins are free of corrosion, if there is a bit of corrosion you can sand it off with fine grit sand paper. You also want to make sure the trailer connector is properly and fully seated with the truck's connector.

If your pins are good and the connectors properly connected, I recommend to test the brake output circuit for 12V on the 7-Way when the vehicle brakes are applied or the manual override is applied which sounds like you may have already done possibly. You should have 12V of power on the brake output circuit when the brakes are pressed or manual override activated.

It sounds like you most likely do not have power on the brake output circuit when the brakes are depressed then you can remove the plug from the factory port and test the brake output circuit there for 12V. If the factory port does not have power at the brake output pin then your fuse is probably blown. You want to check fuse location F30 (this should be the trailer tow receptacle fuse) in the power distribution box for a blown 30 amp fuse and replace it if needed. Then check the F11 location of your power distribution box in the truck to make sure the integrated brake module 30 amp fuse is not blown. (If equipped with integrated brake control).

If you have power at the factory port your 7-way plug needs to be replaced with Curt 7-way plug # C55774.

expert reply by: Heather A