I bought a 97 f150 Lariat a couple of months ago. It has a factory towing package with the 7 pin outlet. I bought a 7-4 pin adapter to tow my utility trailer but just got running lights. I checked the harness under the truck and I have power to all the small terminals that control the turns, running, brakes etc. The 4 larger terminals the power brakes, backups etc for larger trailers have no power. When I follow the wires, the only one that goes directly to the 7 pin is the running lights, the rest that I need go up to the lights themselves. What I want to know is if I have to add fuses or some kind of kit from Ford to get the 7 pin to work. I have checked for bad fuses under the hood and they were all ok. If anyone can help me out I would greatly appreaciate it.

 

You need a brake controller for the brake circuit, and relays for the backup and battery charge circuits. The relays get installed in the PDU box under the hood.
The battery circuit is hot only with key-in-ignition-on.
With many brake controllers, the brake circuit is hot only when: A) moving and brake is depressed, ie, very little or no power when stopped, or B) the controller slide switch is activated.

Lots more information if you search for it.

 

I question whether you really have the towing package because it sounds like a cobbled up job to me. My truck didn't have the towing package; it came with only a 4 pin. so I bought the Ford 7/4 pin (the Ford product should have both a 7 pin and 4 pin outlet type). It plugged right in; in place of the original unit. Then I added a relay and fuse under the hood for battery charging. If you want backup lights or trailer brakes; you will need a brake controller and possibly some more relays/fuses. If I were you, I'd start over by yanking out the cobbled up job and get the Ford parts. They plug and play. Very easy to do and inexpensive. I'd bet that your problems would go away. but check your owners manual for the relays/fuses and make sure you have them and that they are "good". I think there is also a "thread" at the beginning of this forum that outlines the circuits for the 7 pin etc. Good luck.