Trailer Brakes and Brake Controller Display Pulsate when Turn Signal is Used

Question:

I have a Tekonsha time delay brake controller that pulses with the left turn signal. Other than that it seems to work good. The only time that I can actually feel the pulsing is when the gain is turned up. The tow vehicle is a 2008 motorhome on a Workhorse chassis. A wiring harness was provided by the steering column for the brake controller but the wire that was provided to connect to the red wire of the controller was not the cold side of the brake switch. The wire was hot at all times. Therefore I spliced the red wire from the brake controller direct to the left brake light wire. When under way with the trailer connected and the left turn signal activated the brake controller readout pulses up to a reading of about 0.4 amps. With the turn signal off and the brakes applied the controller reading goes up to about 4.5 amps. Is there a fix for this problem?

asked by: Steve S

Expert Reply:

You will need to splice into the correct wire for the brake controller red wire. The issue is probably related to a shared turn signal/brake circuit. Since you tapped into that circuit the brake controller is going to apply the trailer brakes when the turn signal is on.

To find the correct wire first locate the brake switch above the brake pedal. Then use a circuit tester like # PTW2993 if you need one, to probe the brake switch wires. Be sure to test all the wires with the brake pedal and also by turning on the turn signals and head lights. You will want the wire that only shows power with the brake pedal and not with the signals or head lights as well.

If you cannot find this wire at the brake switch then you will need to locate a dedicated brake light circuit somewhere else. Check the owners manual and fuse box lid for the location of the stop light or CHMSL circuit. These are dedicated brake light only circuits. You can then use a fuse tap and run the wire to the brake controller.

If this issue continues to happen then using a pulse preventer, # 5501, should take care of the issue.

expert reply by: Michael H