I recently bought a 2003 F250 which has the light switch for the fog lights (pull out for fog lights) but no fog lights were installed. Under the front bumper near the L/H towhook are 3 wires coming out of a loom that look as though they were cut off. Two are tan with orange traces and the third is black with what looks to be a part of a splice. I was hoping these were the factory wires for the fog lights, but there is no power to them when the light switch is turned to headlights and pulled to the fog light position. I've checked the fuse, it's there and good. I did a search on this and there was mention of a fuse/relay box under the hood. The only thing I found was just next to the master cylinder were 2 relay boxes, the larger having space for 3 fuses but only 2 installed. There is no mention of these fuses or their function in the owners manual. Could the missing fuse here be the one for the power to the lamps? Anyone know of a service manual with wiring diagrams for this year truck?

Are these wires really the fog light wires and if so, where should I look next for a continuity problem? Are the fog lights readily disabled at the switch? The fog lamp indicator lights when the switch is pulled.

 

the two boxes next to the main underhood fuse box and for relays. the one closest to the fuse box are for the "traiiler tow back up lamp relay" and the "trailer tow battery charge relay"(#38 and 39 in the owners manual) the one towards the front of the fuse box are the 2 "shift on the fly relays". in the under hood fuse box, fuse # 12(upper right hand mini fuse, 15 amp) is for the fog lights and daytime running lights. there is also a fog lamp switch fuse(#31 in the under dash fuse box) it is the fuse on the lower right hand side(5 amp)

 

My owner's manual lists fuse #43 as the fog light fuse at 10 amp rating. edit:This is in the underdash fuse box.:

The only mention of a fuse under the hood is for the "FICM logic 15A mini-fuse is locatedin the underhood relay block." They provide no clue as to where the relay block might be. I can find no indication of the presence of an underhood fuse block other than the two relay/fuse boxes previously mentioned. This is a 2003 F-250.

 

my info is from a 2001, i guess they changed the fuse boxes(odd). sorry it souds like yours is completley different. as far as the info i have there is no user replaceable relay for the fogs

 

Well, anyone else want to take a stab at solving this mystery? I'm baffled without a wiring diagram. Ripping open all the harnesses just to trace wires without knowing their purpose would seem my only option. Open to suggestions.

 

On my 2001 there is a relay cluster under the dash just above the glove box (top right). The box on my truck got wet from a windshield leak and it affected the daylight running lights and low beam headlights. On the 2001 the daylight running lights and fog lights are on the same fuse, so may also be on the same relay. Might be a place to check.

 

One thing you can do to tace the wire is get you a wire toner and trace them with it. You can get one at Home Depot for around $60 bucks use it and bring it back(just kidding)(no I'm not). It will let you tone the wires atleast from the underhood side to the break/stop in the wires. Just my .02