Trailer Brake Controller Shows Constant 12 Volt Power After Wires Corroded and Blew Fuse

Question:

I have a 1997 Chevy Suburban with a Tekonsha Voyager brake controller. I found the charge wire constant 12V and the brake wire had both corroded at their connections about 12inch from the plug at the back of the truck. The charge wire had blown the 30 amp fuse in the fuse block under the hood. I have wired them back up correctly but now I have a constant 12V at both the charge contact in the plug and the brake contact in the plug. There is a constant 12V coming into the brake controller through the black wire from the fuse block and a constant 12V going out the blue wire from the brake controller. All without the brake pedal pressed or the controller operated manually. The red wire from the brake light switch only has 12V when the pedal is pressed as it should. When I disconnect the black wire from the fuse block to the controller there is still 12V present in both the black and blue wires, but if I leave it disconnected the voltage slowly fades to 0 in about 15-20 minutes in both wires. Is this symptomatic of a bad controller?

asked by: Jim B

Expert Reply:

You could have a bad controller or the original short that blew the fuse also damaged the controller. And you could also have another short or not totally fixed the original issue. To test the controller, cut the blue wire a few inches back from the controller. Then use your tester to test the end coming out of the controller. If it shows power without the brake or manual override then it is a bad controller and it will need to be replaced.

Also check where the original problem occurred. The corrosion could have spread beyond where it has been fixed but not be visible. Replacing everything or finding and isolating the affected areas using your tester would take care of that issue.

You will also want to check the vehicle side trailer connector and make sure there is no corrosion on the pins or where the wires attach. I have included a couple of links that should help you.

expert reply by: Michael H