I have a 97 expy that i have had the problem more than once. At the top of the brake pedal where the master cylinder rod meets up is a switch with two? three wires, anyways the green one usually is the culprit of a bad connection. The switch can be removed easily by removing the cotter pin. The top of the switch also comes off- its easier of the pedal- by depressing the dog ears on the sides of the switch. The connector can be reused if you don't have one handy The best solution for me was to solder the wire and connector. The connector in the switch can be removed by depressing the tab inside th end of the connector. This same thing occured on my 90 bronco. Hope this helps you all! I'm still learning how to reply to these posts and still don't have it down, so sorry

 

dude, i had the same problem before & it took me a while to figure it out......thanks for sharing the info