Troubleshooting Primus IQ Trailer Brake Controller with Blank Display

Question:

I installed primus controller in 2003 gmc truck with harness and everything seemed ok. The numbers and letters in the display seemed chopped off so I pressed the manual button without trailer hooked up and now nothing in display Thanks

asked by: Randy

Expert Reply:

Applying the manual override lever on a trailer brake controller like the Tekonsha Primus IQ # TK90160, with or without a trailer connected, should do no harm to the controller itself. This action could potentially damage the controller only if there were a bad short in the wiring or corrosion in the trailer connector.

You can test the controller if you have a circuit tester like # PTW2993. First, test the black wire at the back of the controller to ensure 12V operating power is reaching it. If not, you may need to replace the circuit breaker on this power feed. If there is power reaching the Primus and it does not light up at all then it is probably damaged internally and should be replaced.

If the controller does light up you can test its output on the blue wire by setting it for maximum power/boost and pressing the manual override. You should detect output power on the blue wire.
If you have 12V power going in on the black wire but no output power on the blue wire then the unit is damaged.

Please refer to the linked articles for more on testing and troubleshooting trailer brake controllers.

expert reply by: Adam R