I can't get my running lights to work on my trailer. I checked the plugs at the rear of the truck for the trailer hook up with a test light and I have power for everything except the running lights. Does anyone have any idea what it could be. I am going on a trip tomorrow and would like to try and get them working before. Thanks in advance

 

What happens if you change fuse #38?

 

I have problems with the pigtail behind the plug on the truck. I have to wiggle it sometimes to get everything to work. I clean it and grease it every once in a while but it still gives me problems.

 

I checked all the regular fuses with a test light and everything was good where exactly would fuse 38 be

 

in the under hood fuse box.

 

I'll check when I get home

 

sorry to butt in on your thread but i am having the same problem. mine is a 03 f 350 4 wd, 7.3. bought a boat and trailer hooked it up and the tail lights stopped working. unhooked trailer. was completely wired wrong but i cannot find a fuse or anything to get the tail lamps working again. fuse box is under the stearing wheel. no indication in the book which fuse it is, tested everything in the fuse box. any help would be greatly appreciated.

 

The fuse box is not inside the cab. All fuses for the engine and running, signal, stop lights are in the under hood box.

The trailer light and trailer battery charging relays are attached to the under hood fuse box. There are separate fuses which feed power to those relays. If connecting the trailer lights turns off the lights, there is a short in the trailer wiring, not in the truck wiring. Use a multimeter to check resistance to ground on the trailer for each power wire going to the trailer if you do not know which wire feeds the lighting. Before doing this, disconnect the trailer pigtail from the truck receptacle. It should not be close to zero ohms in the resistance mode. Trailer wiring can be difficult.

Another cause of no trailer lights-a bad ground. Find the ground connection for the pigtail, it will be close to the hitch. Remove and clean any corrosion, apply a small amount of light grease or Vaseline, use un-rusted bolt to reattach the ground wire. Look also for bad/corroded splices in the pigtail to trailer wiring for the lighting circuit. Larry

 

The underhood box is behind the air cleaner at the driver's fender.

 

I have brake lights and blinkers just no running lights I will check when I get home I'm hoping to find a bad fuse

 

My '01 f250 has the under hood fuses, but my '02 Excursion doesn't. I assumed that was a model year change, but maybe the Excursions are different.

 

Ok just checked under the hood there is a small black box behind the air cleaner with 3 big fuses in it which one is the 38

 

for future reference, my 03 superduty has two small boxes under the hood behind the air cleaner. one box has ( 2) FOAB-14B192AA in it and the other has (1) FOAB-14B192AA and (2) F57B-14B192-AA in it. the rest is under the dash to the left of the stearing wheel. 48 fuses, 10 relays,and 16 larger fuses the you can see into. dont know what they are called. i have tested all of them at lest 4 times already. i'm thinkin there may be a relay tripped somewhere . if in fact there is one. dutch

 

I had an 06 before this truck I have now and a fuse under the dash would always blow causing this same problem but I checked everyfuse and nothing

 

Starting in 2002, the underhood fuse box was discontinued and all fuses were moved to under the dash. There are still a couple of relays under the hood, but the (much easier to mess with under the hood fuse box for trailer lights and such) is gone.

If you need the location of fuse numbers, check your owners manual. If you don't have a manual, you can download one from Ford here Owner Manuals | fleet.ford.com

According to that downloaded manual, on page 180 it lists, fuse/relay location 38, 20 amp, Trailer tow park lamps. For the diagram of the fuse box showing fuse locations see page 178. It shows the bottom row of fuses start at fuse #48 on the bottom right hand corner, so counting 11 fuses to the left will give you fuse #38