Troubleshooting 12V Power on Blue Wire for 2019 Ford Flex Brake Controller

Question:

I have a 2019 Ford Flex which has a factory installed tow package. I installed the CURT 51436 Quick Plug Electric Trailer Brake Controller Wiring Harness which easily plugged into the Flex. Without the brake controller plugged in , I get 12 volts on the black wire. Tested the white wire for ground.... good solid ground. The red wire indicates 12 volts only when the vehicle brakes are pressed. The blue wire nothing. Brake controller plugged in, I get the same as above except for there is 12 volts coming through the blue wire without the vehicle brakes being pressed or the manual control on the brake controller being pushed. Everything Ive read pointed to a bad brake controller. I went through 3 CURT 51110 Venturer controllers and 1 CURT 51120 Discovery. All 4 controllers acted the same as described above. All 4 controllers cannot be bad.... can they? They were bought new. Could there be something in my vehicles system causing this problem? I was wondering if this issue was ever brought to your attention in the past.

asked by: Rick C

Expert Reply:

It's always possible, though very unlikely, that you received 4 bad controllers, but since this is pretty much out of the question it's worth looking at the wiring on your 2019 Ford Flex to make sure everything is in good shape.

Sometimes a brake controller will pulse some power back to the trailer to check if it is connected or not but it sounds like you're seeing full braking power being sent back to your trailer.

I recommend checking the connector on your Flex that the controller plugs into and the wiring adapter you're using. If either of these has a short or some damage then they could easily be transferring the 12V power from the black wire pin over to the blue wire pin. If that all looks good then I recommend taking your vehicle in to a Ford dealer to see if they have come across this in the past, as this isn't a common issue that we know of.

expert reply by: Jon G