No Power from Ford Brake Controller to 7-Way Trailer Connector on 2010 Ford F-150

Question:

just installed new in dash ford tbc on my 2010 f150. installed fuse and relay that came with unit, hooked up trailer and did not have trailer brakes. checked power to tbc, good. tried again, still no power to 7 pin plug on truck. checked continuity of blue wire from dash to 7 pin, good. jumpered red and blue wires inside of 14 pin plug behind dash, tested 7 pin- whalla, had my 12+ volts. reinstalled tbc, once again nothing at 7 pin at rear of truck. I jumpered tbc with test leads while tbc was out of dash and I get 12+ volts on what would be the blue pin on back of ford tbc. but when tbc is plugged into 14 pin connecter I do not get any voltage at all in my 7 pin, what is happening? it is as if my red, blue or both pins on back of tbc are not making contact inside the 14 pin connecter. tbc part number is AL3Z19H332AA.

asked by: TIM

Expert Reply:

I think this might be the ultra-rare Ford dummy harness issue. A few years ago I had a customer with a similar problem. It took days of troubleshooting and a savvy Ford tech at a dealership to determine that the harness behind the dash that the controller plugs into was not a complete harness so that could be what is going on. Ford would have to provide the harness.

If you have the correct harness, which is likely given how rare this issue is, then it could be another problem with bent or broken pins in a connector.

Otherwise there are some tests you can do to determine if the brake controller is the problem. In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override or brake pedal. 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. Then move on to the truck side trailer connector. Many times, dirt or corrosion can cause a short in a trailer connector. Make sure the truck and the trailer side connectors are clean and free of corrosion inside and out.

You can test the brake output pin 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.

If this isn't the issue then since you mentioned it is the Ford controller you will need to have a Ford tech take a look at it.

expert reply by: Michael H