Troubleshooting Trailer Lights and Brakes After Rainstorm

Updated 07/11/2018 | Published 07/09/2018

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(196)

$75.02

Curt T-Connector Vehicle Wiring Harness for Factory Tow Package - 7-Way and 4-Pole Flat Connectors

(735)

$36.94

Hook Probe Circuit Tester

(66)

$14.86

Question:

Background. About 2 weeks ago my trailer plug was lying on the ground during a rainstorm. Water ran out of it when I picked it up, but like a doofus, I went ahead and plugged it in. Now I have no power to the back of my truck. The brake controller lights up when brakes are applied, but it appears the brakes are not working. None of the lights work either. I use two trailers with the same problem on both, so I am assuming the problem is from the receptacle on the truck forward. There is one exception on the lights. The newer trailer has LEDs and the daylight running taillights seem to work, although after dark the regular tail lights do not work. I have checked F10, F36, F42, F105. All Checked good. I have not checked any relays. The only way I know to check is to replace.

asked by: Steve

Expert Reply:

Since the issue you are describing after the rainstorm is the same on two different trailers, it definitely appears to be coming from your Ford F-150. With that being said, I still recommend using a circuit tester like # PTW2993 to test the pins on the truck's 7-Way for function. Have a buddy run through the light functions in the cab while you test the pins. If you don't get any power, then you know for sure the problem is on the truck.

Since water got into connector, I recommend inspecting it for any rust or corrosion that you see built up around the pins, cleaning out as needed. You can then use the circuit tester again to test the wires going into the back of the connector to see if you get power there. It's possible that just the connector itself is bad and you will only need to replace it with one like # HM40975.

If the wires going into the connector don't have power either, try unplugging the harness from the factory US connector under the truck and testing the pins there. If you get power there, then you can replace the connector and plug-in harness with the Curt # C55774.

If you still cannot resolve or find the issue, please let me know and I will be happy to look into this further.

expert reply by: Chris R