I have a 1998 Ford Expedition. It would shift out of park. I determined that it was the brake light/shift lock switch so I replaced it. Still wouldn't work. Determined of all things that it was a fuse. Replaced it and it work fine for about 2 weeks then the fuse blew again. I replaced the fuse and it blew immediately... anyone have any ideas why? Thanks.

You could have a short near brake lights, from there it goes to signal head, then brake switch.
Try your 4 way flashers and walk around vehicle noting that all work.
If Flasher fuse blows, problem likely between Signal head and Brake light bulbs.

Do you have trailer wiring? Check for any broken/damaged wires and any corrosion on the connector.

I have a 1998 Ford Expedition. It would shift out of park. I determined that it was the brake light/shift lock switch so i replaced it. Still wouldn't work. Determined of all things that it was a fuse. Replaced it and it work fine for about 2 weeks then the fuse blew again. I replaced the fuse and it blew immediately...anyone have any ideas why? Thanks.
Mingo, I am having the same issue with my 2002 excursion and found the fuse blown as well.When replaced, it immediately blew. I also replaced the brake on/off switch and all was fine for a week, then bam, again same problem. I then un-plugged the entire trailer harness underneath the rear bumper and again, I replaced the fuse and it was OK for a day. I went to leave for work the next morning and again I could not get it out of park and yes, the fuse again was blown. I am still searching for the cause and am assuming it is a short. All brake lights are functional and see nothing out. Would appreciate any findings you may have with your problem and I as well will get back to you when the issue is resolved on my end. Thanks !

If the fuse blows when pedal is pushed then it is likely from pedal to signal head then brake lights. If it blows without pushing pedal, short is before brake switch.
Amasky, I'm guessing you have more than 2 wires on brake switch. Due to the fact, your fuse blows, AND brake lights work.

Yes I do have more than one wire off the BOO switch. Still working on this ! I am assuming there is a short near the rear end somewhere.

Yes I do have more than one wire off the BOO switch. Still working on this ! I am assuming there is a short near the rear end somewhere.

I thought you posted over a week ago that you had already fixed this problem..

I thought you posted over a week ago that you had already fixed this problem...?
Well so I thought.. Like I said, problem was all set for a week then again same thing..

Definite short somewhere. Unfortunately for you, you must begin tracing wires(major headache).

Do you have more than 2 wires on Brake switch?

Do you have more than 2 wires on Brake switch?
Yes there is. Has a harness that plugs in the BOO switch