Check this out, might a good deal for someone. Not my truck but I stumbled on it and thought I'd pass it on. I don't know if its a gasser or a diesel. Might be a scam too.
d1999 ford expedtion for trade - $1 (green bay)...
Is your truck chipped? maybe when you step on the brake, you are hooking the wire for your chip and pulling it a bit with your foot. Make sure the cable is up out of the way and secured in place.
If the alt is bad, check the batteries right away too. I had an alternator burn out because I had one bad battery. I replaced both batteries and the alternator at the same time and no more problems after that.