Tekonsha Primus IQ Trailer Brake Controller # TK90160 Shows No Connection to Trailer  

Question:

Expert Reply:

Your Tekonsha Primus IQ # TK90160 brake controller will display the NC message (indicating the trailer is not connected) for any of several possible reasons: if the trailer is not connected, if the connector has corrosion, if there is an open circuit on the brake line, if the trailer brake magnet loses its ground connection to the trailer frame or if the brake magnet is malfunctioning.

Although trailer lighting functions are carried on the same 7-way connectors, since they are on separate circuits it is entirely possible that the trailer lights can function correctly while the brake circuit does not. You do not mention whether the trailer brakes are actually operating; if the trailer brakes do engage when you press the pedal and the display still indicates NC then the unit may be damaged. If the trailer brakes do not engage then I suggest you take the following troubleshooting steps.

First, you want to isolate either the vehicle or trailer as the source for the problem. Use a circuit tester like # PTW2993 to test the brake output circuit at the vehicle 7-way to confirm there is a brake signal. (If you have access to another tow vehicle or trailer known to function properly you can try substituting to see if the problem remains.) If your vehicle 7-way has a brake signal on the brake circuit pin (the pin at the 5-o-clock position; see photo provided) then there may be an issue within the vehicle wiring. Next apply your tester to the blue wire at the back on the Primus; apply the brake pedal and check for an output signal from the Primus. If it is generating an output signal then there may be an issue in the vehicle wiring between the brake control and the 7-way.

Next check the vehicle 7-way and trailer 7-way connectors for any signs of even slight greenish or whitish discoloration on the electrical contact surfaces. Corrosion does not always appear as actual rust or encrusted metal. If in doubt clean the contact surfaces; if there is any significant corrosion of the contacts, or if the connectors have been in use for many years, you might replace them. For the vehicle side you can use Hopkins # HM40975; for the trailer side you can use either the 3-foot Hopkins # H20042 or the 8-foot part # H20046. If the connectors are ok then move on to the trailer wiring.

Trace the blue brake circuit wire and the white ground wire from the trailer connector all the way back to the brake assemblies. Look for worn spots or cracks in the insulation; make sure no wiring is rubbing against sharp edges of the trailer structure and that it is routed away from moving suspension components.
Ensure the white ground wire is tightly secured to a clean bare metal spot on the trailer frame. Repair or replace damaged wires as needed.

Next check the wiring at each of the trailer brake assemblies. Each brake magnet must be solidly grounded to a clean bare metal surface; the other brake wire connects to the blue brake circuit wire. Make sure both wires are connected securely at each brake.

I have linked you to an article concerning troubleshooting brake controller installations and several videos that might be helpful to you.

expert reply by: Adam R

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