How to Test Tekonsha Primus IQ Brake Controller that Stopped Working

Published 03/08/2019

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16 Gauge, 4 Conductor Jacketed Wire - Per Foot

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Hook Probe Circuit Tester

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Question:

Hello I have the Primus iq not sure which model it is. My trailer lights all work , but I get no voltage at the blade terminal for the electric brake. I unplugged the controller and used a jumper wire from the black wire to the blue wire and then I see voltage at the blade terminal at the trailer connector.I also checked the wire for continuity from the plug at the controller to the blade terminal at the trailer connector and I get 0.06 ohms. Is the controller no good?

asked by: Carey L

Helpful Expert Reply:

Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part # PTW2993, you should get output to the controller side of the wire you severed. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly also then the problem is farther back either in the vehicle wiring or on the trailer.

If either the brake pedal or the manual slide are not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire. On the red wire you will only want power when the brake pedal is pressed.

If there is power on the red wire before the brake pedal is pressed you have connected the red wire from the brake controller to the wrong circuit. You would then need to find the brake switch wire that has power ONLY when the brake pedal is activated.

If these connections check out and the brake controller is properly grounded then there is possibly a problem inside the brake controller.

I am including a link to a video that will show you how to test the wiring on a brake controller.

expert reply by: Jameson C