Wiring Electric Trailer Brakes with Magnets that Have 2 White Wires

Updated 04/14/2014 | Published 04/13/2014

Question:

My trailer has brakes on 2 of the 3 axles. Each brake hub has 2 white wires and the axle has 1 red wire and 1 black wire. My question is this...which wire connects to which wire? I have a blue wire from the 7 pin connector and a black wire from the 7 pin connector. The blue is for the brakes and the black is for 12V. Not sure which of the axle wires goes to which of the hub wires and then which goes to brake and which goes to 12V. Got all the lights working, but my 2012 Chevy 2500HD says service brake system soon when the trailer is connected. Thanks!

asked by: Dave B

Expert Reply:

It sounds like the magnets or their wiring could be bad. Your 2012 Chevy Silverado 2500HD is probably sensing the wrong resistance from the trailer brake magnets and that is why you see that warning message.

When magnets have 2 of the same color wire it usually means that you can use either one for either function.

The black wire with the 12 volt power should not be attached to the brakes. Only the blue wire should connect to the brakes. The other magnet wire should be attached to the trailer frame near the magnets. Attach the ground wires to a clean and corrosion free bare metal surface.

You can do some tests on the brake magnets to see if they are ok. Start by visually inspecting the magnets and if you can see the copper windings coming through then the magnets will need to be replaced.

To further test the magnets you can follow the help article I have linked for you.

expert reply by: Michael H