[fuffl]

OK. Here's the deal. I've got a 71 Chevy 3/4 ton pickup for a winter driver. I had to hit the brakes hard last night to avoid some doofus on his cell phone. It turned my brake idiot light on. The truck still stops fine, the fluid is full, and I checked every brake line on the vehicle for a break or leak...but found nothing.

So, my question is. What other things can trigger the light on such an old vehicle. The sensor system must be pretty simple.