Tekonsha Primus IQ Shows Voltage Without Trailer Connected

Updated 03/14/2019 | Published 03/13/2019

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Question:

I purchased a vehicle with this brake controller already installed. When I am sitting in my vehicle no trailer attached currently reading 0.9. As u drive the numbers are constantly changing on and off the gas and we have used it with our snowmobile trailer attached and brakes controller not working. Can this be corrected or junk it and get a new one?

asked by: Darin W

Expert Reply:

I didn't catch what vehicle you were using the Tekonsha Primus IQ Trailer Brake Controller part # TK90160 on but what I recommend you do is cut the blue wire from behind the controller and then turn up both the boost/gain to the max settings. Then once the settings are set to max apply the manual override and test the blue wire with a multimeter. It should show 12 volts here but only when the manual override is applied.

If it doesn't show 12 volts or does so when the manual override is not applied then odds are the brake controller is bad or you have a faulty connection with the stop light switch. If the stop light switch wire looks good then replace the controller. I recommend using the Tekonsha Prodigy P3 Trailer Brake Controller part # 90195. The main difference between the Primus IQ and Prodigy P3 is that the Prodigy P3 gives you the ability to store settings for up to 5 different trailers.

If you get 12 volts when testing the blue wire behind the controller with only the manual override applied then you most likely have a short on the blue brake output wire that runs from the brake controller back to the 7-way trailer connector and it will need to be traced to check for shorts or replaced with part # 10-1-1 (per foot).

expert reply by: Conner L