Tekonsha P3 Short to Battery Error When Trailer Is Connected to 2012 Holiday Rambler

Question:

I am trying to install the Tekonsha P3 brake controller to a 2012 Holiday Rambler 36sbt MH. I bought the connecting harness and connected it as instructions indicated. My turn sig / running lites/ brake lites work, but I when connecting the 7 way plug, but I get the error message short to battery no brakes when connected to the P3. I hear the brakes on the trailer activating humming when I apply the coach brakes, but have the error message. The P3 was taken off of my class C Jayco and was working fine at that time.

asked by: Mark

Expert Reply:

It sounds like there is a short or mis-wired trailer connector since the error happens when you plug in the controller. First, disconnect the trailer and use a circuit tester such as # PTW2993 to test the wires on the controller. The black wire should have 12-volt power into the controller. The red wire should only have power when the brake pedal is pressed.

To test the blue wire, sever it a few inches back from the controller. Use the tester to test the end of the blue wire coming from the controller. It should only show power when the manual override is pressed. If it shows power at any other time then there is an internal problem inside the controller and it will need to be replaced.

If it checks out ok then reconnect the blue wire. Next check the vehicle end 7-Way for dirt or corrosion inside and out. Then do the same with the trailer side connector. Make sure the power wires leading to the brake magnets are in good shape. A broken wire touching metal will cause a short.

The magnets themselves could also be bad. Visually check them and if you can see the windings coming through they will need to be replaced. To further test the magnets you can follow the FAQ article I have linked for you.

It is also possible that the vehicle side 7-Way and trailer 7-Way are not pinned out the same. I have included a link to our FAQ article on wiring that includes diagrams showing the typical pin out for various trailer connectors.

expert reply by: Michael H