I had a similar problem with mine but it turned out to be a dirty connection with the pressure switch. My advise to you is take the time to learn how this system works by going through the troubleshooting procedure. Too many people have ignored that brake light and have paid dearly out of their pockets.
A question to others out there:
Is the "A" and the "B" the wrong way around on the brake switch diagram above, posted on gnttype.org? I think it is, at least according to the labels on the connectors on the car.