My 1986 Ford F-350 cab and chassis 4x4 with the 6.9 idi and t19 4 speed manual has no brake lights or hazards. Based on some tests/diagnostics I did there is no power to the brake light fuse in the fuse box. It seems like if I can get power to the fuse, the problem should be fixed. This problem happened after I did some repairs to the truck - put new battery cables in, injectors in, fuel tank, lines etc... I didn't remember pulling any wires or anything. I did jump start the truck after the repairs though so I wonder if I fried something... Before I did all these repairs, the brake lights and hazards worked flawlessly. Does anyone have a wiring diagram, or can tell me how the fuse for the brake lights gets power? I saw a purple wire with an orange stripe and red wire with a white stripe coming out of the back of the fuse box where the brake light fuse is.

Edit: The truck also has no reverse lights - which was the case before the brake lights and hazards went. Thought I would add this just in case it is tied together.

Thanks

 

Check the grounds at the rear of the truck. Do the parking lights work?

I'm not sure on exactly what the 86 trucks are like, but on my 88 there are a bunch of fusible links coming off the starter relay (battery feed). Check to see if any of them are burnt out.

 

I will look into the fusible links. Pretty much everything works right down to the parking lights, headlights, hi beams, cab roof clearance lights, turn signals, horn, heater, low range indicator light etc - when I got the truck most of these things did not work until I fixed them - the previous owner butchered the harness pretty well.

At first I suspected that this hazard/brake light issue was a bad ground, but with all the other things working, it seems unlikely - but I am not an electrician.

Thanks

 

because you have no power to that fuse, i say you found your problem. if you don't find something obvious with the fusible links, all you should need to do is run a fresh wire to the back of the fuse box at those fuses and you'll likely be up and running. note that the fuse box on these has 2 or 3 fuses coming off of one wire into the box, so you'll likely only have to run fresh wire into one point and it'll be fixed.

i don't know how much you know about basic wiring theory, but i would suggest using a 14ga wire, with a fuse or circuit breaker of 20-30 amps as close to the distribution block (or starter solenoid, battery, etc) as possible. this is to protect the wire in case it shorts out before it reaches the fusebox, same idea as the fusible links.

 

I'm not sure how the power gets into the fuse box, but I'd think you should be able to jumper off another place on the back of the fuse box to where that fuse is. Maybe see if you can pull the fuse box out enough to look at the back of it and see if something is broken.
A few people have posted wiring diagrams in the past, if you're lucky search can find them and that might help you out some.

 

Hey, I fixed the problem, as it turns out someone had the power wire for the brakes and hazards just wrapped on the starter solenoid - no connector. I found it, put a connector on it and it works perfectly. Took the truck on an 80 mile trip today with no issues - the truck sat for ten years until I got it.

I appreciate the all the help.

Thanks

 

time to start looking at what other high-school wiring jobs happened here. pull on every aftermarket connection you see, and if they come apart, redo them right

 

hi i have a 1988 f 250 7/3 c-6 trans fule is killing me what trans would bolt to it like 3 with o/d or a 4 with o/d .jackdaw

 

Great information, same brake light problem. Will check grounds and fusible links.
Thanks.