Troubleshooting 7-Way 12 Volt Trailer Wiring Circuit of 2007 Ford Expedition Not Active

Updated 09/18/2019 | Published 09/17/2019

Products Featured in This Question

Pollak 7-Way to RV Socket LED Circuit Tester - Vehicle End

(160)

$44.57

10 Gauge Wire - Blue Primary - Per Foot

(108)

$1.61

40 Amp In-Line Circuit Breaker - Perpendicular Mount Bracket

(98)

$9.89

Hook Probe Circuit Tester

(66)

$14.40

Question:

For some reason the 7 way trailer outlet auxiliary wire wont work. For the interior lights on my trailer. Ive checked all the fuses on the right lower passenger side box. Even under the hood fuse box. They all work. How can i find out which of the black square fuses might be for the auxiliary. Ive hooked up the 7 way outlet of the trailer to a different ford truck. The auxiliary wire on the trailer works once its hooked up to that 03 F250 truck. But not on the expedition... What could be the problem... I bought this connection and sorted out the wires as how they should be connected for my trailer. This new connection is way different with red being a turning light color... Ive used green and yellow as my turing colors for left and right..brown for the tail lights and yellow from this new connection box as back up lights and black as my auxiliary wire...

asked by: Joe

Expert Reply:

First thing to try is cleaning the pins on your 2007 Ford Expeditions's 7-way as a bit of corrosion on the 1:00 pin notoriously kills the 12 volt accessory circuit. I believe this is most like the issue since you said all of the fuses are good on the vehicle. You can also check for voltage on this pin with a circuit tester like # PTW2993.

If the pin is just dead and you've tried with the vehicle running and the key on (sometimes this is only way this circuit is active) then easiest solution is to run your own wire to the battery from the 7-way circuit with 10 gauge wire like part # 10-1-1 (sold by foot) through a breaker like part # 9510 to bypass the OEM wiring and get the circuit going.

expert reply by: Jameson C