Those are stop / turn lamp leads in the 4 pin & 7 pin trailer tow adapter.

If you have power at all times, do you have brake lamps that are stuck on ( check on the truck ).

If the truck's brake lamps are fine, next is to check if the MFS ( Multi Function Switch ) is enabling the coil on the relay, or if the relay is stuck in the closed position.

Pull the 2 relays for the Left & Right stop / turn ( left side of the Power Dist relay box ) and check with a meter on pins #1 & #2 for + VDC.

Ignore the red line ( that is for a different test ), just use some small wire to extend the meter leads into the relay socket, and take a reading on DC Volts on a meter.


If you are sure you are making contact with the terminals, and do not get battery voltage ( i.e. `12.6 VDC ) then the relays are stuck in the close position and both need to be replaced.

If you are getting + VDC on pins #1 & #2, you have an issue with either the MFS or the BOO Switch ( Brake On/Off ) / BPP Switch ( Brake Pedal Position )
- ford called it the BOO in the 97-98 MY, 99 it was changed to BPP, but same thing. Might also be commonly refereed to as the Brake switch by some.

 

I bought my '97 F-150 in Feb of 1996. I had not had any problems until this past spring. I aquired a 16' trailer and used it 2 or three times. My golf car trailer hadn't had any problems either. Then, all of a sudden, last March, neither trailer turn/brake lights would work. I ask friends and they said ground or fuse. I took it to the local shop I use and he checked for power and told me I had power in the plug-in by the bumper. We found no fuses burned out. This was last spring. I still have my owners manual in the glove box and it shows all (?) fuses and I checked the ones it said. I have a check light and could not get a turn or brake power to light it. Then this week, I got the golf trailer rewired. Still no turn or brake but had "running lights". I googled '97 F-150 towing pkg wiring diagram but ended up on this forum where I found the answer to my problem. I found the small fuse box with a 5 and 20 amp fuse in it. The 20 Amp fuse was blown. Changed the fuse and all brake and turn lights now work properly. This small fuse box is not listed in my owner's manual. It's a good thing Ford did adding this fuse box as it protects the vehicles brake/turn signals. The larger trailer is the cullprit as it has a "short" in it's wiring which "blew" the fuse.

Thanks for posting the info on this unlisted fuse box.

 

Thank you for posting your symptoms and that the solution was the same one.

This will help the next member when doing keyword searches, to find the thread.

Glad things were as easy as one fuse, after repairing the trailer wiring.

 

This thread is a lifesaver... the previous engineering firm that owned the truck 97 Ford F-150 4wd 4.6L had tapped into the rear stop/turn wires to make them work with a 4 pin connector, the 7 pin connector only had running and trailer brakes working. The problem was in the "hidden small fuse box" that had a blown fuse for the trailer stop/turn. Thanks for keeping me from having to trace the wires all the way up the frame.