I got a 2003 F150 a few weeks ago. It blew the #13 fuse a few days ago and will immediately blow the fuse when I replace it. The not hot side of the fuse connector has 1.274K ohm resistance. I unplugged the BOO switch connector and there's 1.274K ohm on the power lead (green/red wire) so the short is between the fuse panel and the BOO switch. I don't have cruise control so no brake pressure switch and didn't see a loose connector for the brake pressure switch. I can't find the turn signal flasher, I read it's supposed to be under the dash near the radio but I can't access that area because the A/C ducts are in the way, I can't hear it click because the turn signals aren't working, the brake lights, hazard flashers and high center brake light also don't work. I pulled on and moved the wires that go to the BOO switch and it didn't change the ohm reading so I don't think it's pinched or grounded there.

1. Can I remove the fuse box to get to the wire to the BOO switch?
2. What else does fuse#13 supply power to?
3. The wiring diagrams in my Haynes manual aren't very helpful. Does anyone have better wiring diagrams?
4. How can I get to the turn signal and hazard flashers?

Thanks for reading this, any help will be greatly appreciated.

 

1. You may well have to if nothing else pans out.

2. BPP switch and the flasher relay. That's it.

3. Try Autozone's repair guide. Registration is required, IIRC.

4: Look up above the gas pedal. Aux relay box #4 has a cover to be removed. The drawing below is for a 2001 Expy which is the same as your 03 F150 for this issue.

 

Thanks for the diagram. I got the flasher out and that got rid of the ground. I still haven't replaced the flasher so I can't say that that fixes it or if the problem is past the flasher. I'm hoping the flasher takes care of it. I can't work on it now though because I'm visiting the kids and won't get back home for about a month. Will let you know how it turns out then.

 

Well I'm back, spent a month with the kids, hit up all our favorite restaurants; gained the 10 lbs. I lost over the past year. Anyway I replaced the flasher and it stiil blows the fuse. Figuring the next thing downstream from the flasher is the turn signal switch I removed that. The fuse doesn't blow with the turn signal switch removed. The switch is put together with screws so is it serviceable? If I take it apart is it likely it can be fixed? Thanks for the help.

 

I am bewildered. I replaced the fuse with a brake lamp I wired in so it doesn't keep blowing fuses. If the lamp lights up there's a short someplace. The brake lights don't work with the turn signal switch connected. I removed the turn signal switch and if I put a jumper between the power from the brake switch to either the left or right brake light it comes on and the test lamp glows but if I jumper to both brake lights neither of them light up but the test light is brighter. I've only had this truck for a few months and it looks like someone has had to work on this before because some of the harness is unwrapped in places where I've been checking and then taped up with black plastic tape. I had a pickup topper put on shortly before this all happened and they put in an adapter for the high mount brake light on the topper but I disconnected that in case that was causing a problem. The leads for that tied into the trailer light wiring but they don't connect to anything now.