My 89 f150 recently started blowing the fuse, 15amp, that also affects hazzard lights and the cruse control release via the brake switch.

I have checked the wiring visibly and see no problem. I recently had the Actuator linkage (shifter/key switch related) in steering column replaced and in my mind the problem seemed to have developed after that but that is only a thought.

 

It's most likely a trailer connector wrapped around the rear bumper or frame shorting out. Does the fuse blow the instant it's replaced, or the first moment you press the brake pedal, or after holding down the pedal for a few moments?

 

It is not the trailer wires wrapped around the bumper for sure. As for when it happens this varies. Sometimes it will not blow for several minutes then it will blow when nothing else is happening that is it will be ok and everything seems to work I will walk away then when I come back it will be blown. Once it seemed to have blown when I turned on the hazard light. I put in a new switch at the brake pedal and thought that fixed it because it didn't seem to blow right away. But I was wrong. I disconnected the brake pedal switch and it still blew. I am leaning toward it being in the part of the circuit that releases the cruse control via the brake switch, but it blows even if I don't use the cruse control.

 

If it blows with the brake switch (BOO) unplugged, then it's not anything to do with brake lights (including the cruise deactivation). That fuse (#1) feeds the R/Wh wire that goes directly to the hazard flasher. If the fault was on the other side of the flasher, you'd hear it clicking constantly until the fuse blew. From there, the Gn wire branches off to the BOO, and you've determined that it's not on the other side of the BOO. So that only leaves the Gn wire being shorted to something under the dash, or something being spliced into it. It's a very short wire, so it should be easy to trace from the pedal back to the fuse block.

 

Thank you for your response, this is what I have found.

I removed the fuse block so I could see the back side and tried tracing the Gn wire from the BOO. It is indeed a short wire that has no splice in it and it goes into a wrapped wiring harness. The #1 fuse has the R/Wh wire as you mentioned and a yellow wire on the other side I didn't see a Gn wire going to the fuse block if that is what you meant by. "It's a very short wire, so it should be easy to trace from the pedal back to the fuse block." Should I unwrap the wiring harness and continue tracing the Gn wire?

 

You don't have to unwrap it. Just unplug the BOO & pull the fuse and flasher, then use a digital multimeter to check resistance (continuity, diode) from one end of the Gn wire to the other.