I have a 97 expedition that has the factory towing pkg. I recently went to plug in my trailer that has always worked fine with this truck and no brake or turn lights but running lights. I checked the fuse under the hood and it was blown. I have replaced it and still no turn or brake lights, just running lights. The fuse is still good, but I replaced it anyways. Still no turn or brake lights but running lights are ok, even with a wire bypassing the fuse under the hood. Now what?

Not to the factory wiring- your not-leave that alone

Get the wiring diagrams & see how the factory
tow pkg was wired & follow that

Ask at dealers parts dept

some van don t have a ground wire. hook up to trailer put jumper cables to frame of trailer and van if works install a ground wire plug

Thanks Syntax Error for letting us know you figured out the wiring harness was wired incorrectly. It is always a good idea to look up the color wiring standard for the socket and to check the pin positions and what functions .
Sometimes trailers can be wired incorrectly also ?
I wired the licence plate bulb to my brown wire by mistake and this is the brake wire . Took a while for me to figure that one out !

Not sure which fuse you checked.
The Engine Compartment Fuse Panel ( Battery Junction Box / BJB ) is where the fuse is for the trailer tow adapter parking lamps.
Fuse # 5 is the fuse for the parking lamps, and the reversing lamps.

Next is the trailer tow adapter park lamp relay. This is what BJB Fuse #5 feeds, and the coil is operated by the truck's parking lamps. This is also in the BJB, Relay 201, it is the 1/2 size relay.

Not sure what you took a resistance reading from on the trailer tow adapter.

If you want, you can pull the trailer tow park lamp relay, and jumper the normally open contacts, which should provide power at the trailer tow adapters, regardless of the truck's lights.


This is the wiring diagram for the trailer tow park lamps

Did you check the fuse for the trailer tow adapter parking lamps ? This is a separate fuse from the truck's parking lamps.
Fuse #10 is the Trailer Tow parking lamps ( via the trailer tow parking lamp relay ) and this is the same fuse for the trailer tow reversing lamps ( via the trailer tow reversing lamp relay ).

If you did not get an owners manual with your truck ( purchased used ), you can download one from Ford :
https://www.fleet.ford.com/maintenance/owners_manuals/default.asp

Diagrams for the Trailer Tow adapter :

There are a few fuses for the trailer tow adapter.

1st, is theodd location on the 97-98, engine mini fuse panel has a 20 A fuse forthe stop / turn lamps. Have seen it covered in tape from the factory onsome 97-98 MY trucks.
This is on page 142 in the owners 1997 manual, all the revisions for the 1998 owners manual I have seen do not include this fuse box for some reason.

Download a PDF version from Ford, for the 1997 MY at :

https://www.fleet.ford.com/maintenance/owners_manuals/default.asp

This is a picture of the Power Distribution Box, additional relay box and engine mini fuse panel with the covers off. The 20A in the upper right panel with the red base, is the trailer stop/turn fuse.


The others :
1. Power Distribution Panel / engine compartment fuse panel
Fuse #1 - Trailer tow back-up and tail lamps
Fuse #16 - Trailer tow battery charge and stop/turn lamps
Fuse #28 - Trailer tow electronic brake

2. Instrument Panel Fuses ( cab fuse panel by hood release )
#23 - trailer tow battery charge relay

There are a few fuses for the trailer tow adapter.

1st, is the odd location on the 97-98, engine mini fuse panel has a 20 A fuse for the stop / turn lamps. Have seen it covered in tape from the factory on some 97 MY trucks.
This is on page 142 in the owners manual.
If you see one, you can download a PDF version from Ford at :

https://www.fleet.ford.com/maintenance/owners_manuals/default.asp

The others :
1. Power Distribution Panel / engine compartment fuse panel
Fuse #1 - Trailer tow back-up and tail lamps
Fuse #16 - Trailer tow battery charge and stop/turn lamps
Fuse #28 - Trailer tow electronic brake

2. Instrument Panel Fuses ( cab fuse panel by hood release )
#23 - trailer tow battery charge relay

check wiring on trailer

went to the dealer for free