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Troubleshooting Curt Fri-Flex Brake Controller Installation in 2014 Nissan Frontier

Question:

Further to my previous question. I have tried road testing the trailer. When I start up the vehicle with the trailer attached the controller calibrates itself then goes into standby mode. If I apply the brakes the controller flashes dc and the trailer brakes lock on and wont release until the dc stops flashing. I have tried this with various adjustments to the controller all with no variation. Needless to say this is driving me nuts.

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Expert Reply:

I suggest you disconnect your trailer and test both the tow vehicle and trailer independently. Please note that if your vehicle's 7-way trailer connector has LED test lights built into it, then the TriFlex brake controller will not be compatible.

First you can check the signals going into and leaving the Tri-Flex. Apply a circuit tester like # 40376 to the black wire at the controller. This wire carries 12V power to the Tri-Flex and should be hot at all times, even when the vehicle is off. The red wire should carry a signal ONLY when you press the brake pedal. The blue wire should carry the controller's output signal only when you press the pedal or engage the manual override. If this is not what you observe then the unit may be damaged.

Next you can test the signals at your Frontier's 7-way trailer socket. Brake controller output should appear on the pin at the 5-o-clock position (please refer to the linked photo) when the brake pedal is pressed.

You might also carefully inspect both the vehicle and trailer connectors for any signs of corrosion. Even slight greenish or whitish discoloration on the contacts can indicate corrosion. It is possible for corrosion to cause two separate circuits to become bridged together; this can cause all sorts of erratic behavior. A dirty of corroded contact can fool the controller into thinking that no trailer is connected.

If the truck checks out okay you can test the trailer brakes on their own by applying 12V power to the pin on the trailer plug that carries the brake circuit. Apply +12V to the brake circuit and -12V to the ground. The brakes should engage fully when hit with the 12V input and should release immediately after power is cut. Make sure all brake magnet wiring is secure; one wire connected to the brake circuit and the other to trailer ground (it does not matter which wire goes where).

The linked articles will give you additional troubleshooting help.

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