My nephew brought his 88 F250 7.3IDI over because he discovered it has no brake lights or hazards. Turn signals, running lights, reverse lights all work normally.
He recently got the truck so he's not sure if they ever worked. I changed the hazard relay behind the glove box with one from another truck and nothing. I measured the hot lead(green wire with red stripe) that attaches to the brake swith at the pedal and it only reads 0.75 - 0.80 volts. On my plow truck that wire reads 12 volts. But I can't see where the wire goes to. There also wasn't 12 volts at the fuse panel. Can anyone tell me what wires in the engine compartment connect to the green/red stripe wire on the brake switch? Can I just run a fused 12 volts from the batteries to the brake switch and eliminate the green/red stripe wire altogether?
Thanks.

 

Anybody . . . ??

 

That would be fuse 1 a 15 amp & since theres no power to it, it looks like you've got a blown fusible link. On most Fords there are 3 or 4 small wire fusible links and the positive battery cable connected together at the starter relay. Make sure none of those small wires are hanging loose in the breeze. If the relay was changed they might have neglected to connect all of them

 

The wire from the fusible link to fuse 1 is solid yellow

 

Thanks 87. We looked at all the fusible links and didn't see any loose wires. The fusible links look like they can't be changed. If the link is burned on the yellow wire, how do you repair it? Can I just run 14 gauge with a 15 amp fuse to the hot side of the brake pedal switch?

 

I think fuse 1 was showing the same 0.70-0.80 volts that the hot side of the brake pedal switch showed.

 

I've never had a bad fuse link so cant tel you anything about replacing them. The guys in the electrical forum could tell you more about that. I think what you do is cut the old one out and solder in a new one.

I dont see why you could'nt run your own fused wire to the brake light switch. Put the fuse at the voltage end of the wire..You should have 12 volts going to the switch

 

looks like fuse 1 to the brake light switch is on a red/white stripe. Take a look at the diagrams at bbbind.com. Sign up for a free account.

 

it's really hard to tell just by looking, usually if the link is burned it will have bumps showing on the link, one way to tell is to give each one of the links a good pull, and if the link stretches you can bet it is burned..

Hope this helps...