Power On the Ground Wires Going to the Brake Magnets

Published 01/15/2010

Question:

when voltage is applied to one wire the ground wire has live votage feeding through it. is this normal ? and if so how does this not cause a short curcit ?

asked by: DOUG T

Expert Reply:

No, you should not have current on the brake controllers ground wire when the brakes are applied and yes it should create a short circuit. It sounds to me as if you have a bad ground or a problem inside the brake controller. Brake controllers have no user serviceable parts inside them so the best action would be to replace the controller. I would recommend the Tekonsha Prodigy P2 Brake Controller part # 90885. This brake controller is easy to set up and is our best selling controller with great reviews by our customers.

If you are checking the wires at the trailer brake magnets and you have power on both the ground and hot wire when the brakes are applied then you definitely have a bad ground. You should only get power on one of the wires going to the brake magnet. It does not matter which wire but only one of them, not both. You need to trace the wires and make sure that the ground wires are securely grounded to bare metal on the trailer frame and that the ground at the trailer tongue is securely grounded to bare metal also. A bad ground at the brake magnets will not necessarily cause a fuse to blow or a circuit breaker to trip because the feedback is not strong enough to break the fuse or circuit.

I've linked you to a brake controller troubleshooting FAQ article that should be helpful.

expert reply by: Robert G