Trailer Brakes Locked Up, Brake Controller Blue Wire Shows Constant 14 Volts

Question

Question:

Hello, I am driving a 2001 Nissan Pathfinder and using the Primus IQ Controller. I was pulling my newer travel trailer this weekend and was going about 5 mph in a campground when all of a sudden the trailer brakes locked up I was not pressing the brake pedal and would not unlock unless the trailer was disconnected from the tow vehicle. Was forced to pull trailer home with another vehicle and it towed perfectly with the brakes working well. I have towed 1000s of miles with the Pathfinder and controller and until now had zero issues. I have tried trouble shooting this and this is what I have found so far. Installed a different controller and am having the same issue. With the controller disconnected, the 4 pin connector exposed at the controller connection point, I am getting 14.2V from the black wire, 14.2V from the blue wire, and 0V from the red wire whether the brake pedal is pressed or not. I am really at a loss on this. Like I said it has worked for years and 3 trips towing the current trailer and all of a sudden the sudden failure and the brakes locking up. One other strange thing that I have noticed is that I typically run in B1 mode with a boost of 48, after the lock up event with the trailer connected, the boost will only run up to 14 and no higher. This may be due to the fact that the trailer brakes are already locked but weird. Please help. I have also checked fuse and cannot find anything.

asked by: Mike

1

Helpful Expert Reply:

It sounds like there is an internal issue with the controller and/or a short on the brake output wire. The easiest thing to check would be the vehicle side trailer connector. Corrosion can cause a short causing constant power draw on the blue wire. Make sure the connector is clean and free of corrosion inside where the wires attach and outside on the pins.

You can also inspect the wiring as far as you can under the Pathfinder. Check for damaged wires with copper touching bare metal.

To test the brake controller you will need to sever the blue wire several inches from the back of the controller. Then use your circuit tester such to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override. If it shows power at idle then there is something wrong with the controller and it will need to be replaced.

If it tests fine then reconnect the blue wire. You can test the brake output pin at the back of the truck and it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to track down.

expert reply by: Michael H

1

Answer 1

Since wire color codes are NOT universal, we always recommend wiring by function, rather than wire color. If you look at the Trailer Wiring FAQ article I have linked you to, you can see some diagrams showing the proper way to wire a vehicle and…

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Answer 2

Provided there is a trailer connected and the brake controller was set to the proper output then you should see voltage on the blue wire when you apply the brakes or the manual override. Without a trailer connected, the controller will not send power…

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Answer 3

You can use a 30 amp fuse if you wanted to. The difference is that a circuit breaker like #38630 or #PK54530 will automatically reset should there be a short or overload. With a fuse you would have to replace it.

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Answer 4

Based on what you listed the closest equalizer we have to what you need is the part #TREQ310. This is 4 inches tall from center of mounting holes and has a distance of 6-1/16 inches from left to right. I attached a picture of the dimensions as well.

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Answer 5

The wires exiting the rear of your controller serve the following functions. The blue wires carries the brake output from the controller, the white wire is the ground, the black wire supplies 12 Volt power, and the red wire is tied into the vehicle…

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Answer 6

The issue is the red wire of yoru brake controller. It's only supposed to see voltage when the brakes are applied which then tells the P3 #90195 to start looking for deceleration and apply proportional braking power. If there is a short on this…

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Answer 7

To determine why you do not have any power on the blue brake output wire, I recommend starting at your brake controller. First, make sure the brake controller is on and receiving power. Most brake controllers have 4 wires, blue (brake output to…

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Answer 8

If you sever the blue wire leaving the P3 controller part #90195 leaving enough room to reconnect it and test the end of the wire leaving the controller with a circuit tester like part #PTW2993 you should see voltage when you slide the manual…

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Answer 9

The wiring color codes and wire gauge recommendations for the Pollak Heavy-Duty, 7-Pole, Round Pin, Trailer Wiring Connector, item #PK11700, are listed below. White - Ground Return - 8 gauge Black - Clearance, Side Marker, Identification - 12 gauge…

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Answer 10

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Answer 11

The difference between the Class II and Class III hitches has to do with their Gross Trailer Weight (GTW), their Tongue Weight (TW), and their Hitch Receiver Size. Class II trailer hitch receivers have a 1-1/4 inch receiver and can be rated up to…

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Answer 12

A 4-Way trailer connector has the basic lighting functions only; running lights, left turn signal and brake lights, right turn signal and brake lights, and ground. A 7-Way has these functions and a 12 volt circuit, a circuit for electric trailer…

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