Troubleshooting No 12V Power on 7-Way on 2006 Ford F-150  

Question:

Expert Reply:

If all of the lighting functions on your F-150's 7-way work, but the +12V power feed does not, the first thing you can check is the relay for that circuit. According to my research the relay for trailer power is a Full ISO Relay and it is in position R05 in the power distribution box. Your owner's manual could differ so it's a good idea to check it.

Another potential cause is a weak ground connection at the 7-way. A weak ground might let some light functions work but not allow the power circuit to operate. Check that the main harness ground wire is firmly attached to a clean bare metal spot on the truck, free of paint, primer, grease, rust etc. You can relocate that ground wire to a new clean grounding point if needed.

Another item to check is the 7-way socket (and also the plug on the trailer) for any signs of corrosion that could be causing a short. If you do find corrosion you can clean the contacts or replace the 7-way with part # 74682.

expert reply by: Adam R

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