Tracing Intermittent Short In Trailer Braking System

Updated 02/13/2013 | Published 02/08/2013

Question:

I bought the Tekonsha P3 controller from etrailer and have installed it in my 2010 Tundra. The control indicated a short. I checked the ohms at each brake and they read in specks at 3.7 to 4 ohms. I hooked up the trailer and let it move forward at fast idle and applied the electric brakes. The first three times all seemed to operate normal and stop the truck using the trailer brakes only. On the forth time the P3 indicates a short and the brakes do not work. I disconnected the trailer plug and read the ohms across the plug ground and the electric brake connector. The meter indicates 2 ohms. Which by most standards 2 ohms would be a short. When you wire two 4 ohms in parallel and read across them wont the reading be correct at 2 ohms?

asked by: Stacy W

Expert Reply:

It sounds like you have an intermittent short somewhere in your braking system. The readings you are seeing are correct, because the short is intermittent.

An intermittent problem can be very difficult to find, but your best bet is to physically examine the brake circuit on your trailer, from the connector all the way to the brake magnets. Look for a pinched wire, or cracked or worn wire insulation that would allow the copper conductor to intermittently contact the trailer frame and create a short. You will also need to pull the hubs to examine the brake magnet wiring inside the brake assembly, once again looking for cracked or worn wire insulation. If your brake magnets are becoming worn, you might begin to see an intermittent short. If you examine the front face of your brake magnets that ride against the inside of your brake drums, and see any of the copper wiring from the interior of the magnet, the magnet is worn to the point that it needs replacing.

expert reply by: Mike L