Curtis 1204 doesn't work - intermittent problem

Took the controller out of Dad's farm EV, a modified EZ-GO golf cart. Opened it up, and couldn't find any burns or blown-up components, but the lower end cap had cracked and sagged open and let dirt in. Not real bad, since it was at the bottom end and somewhat self-cleaning. I have blown out the dust and am ready to put it all back together. Now, I am thinking the problem lies in the high-pedal disable feature of this controller. Before removal, I had checked voltage at the input and output terminals, and determined that as the pedal was depressed, input voltage at the controller dropped as if there were a load applied, but there was no output voltage except for a very small surge, then nothing. Occasionally, the surge was just enough that the vehicle could be felt to "try" to move, then stop - all proportional to the readings at the output terminals. Voltage at the inputs dropped to about 12v (this is a 36v system) and stabilized until the pedal was released. Is this normal behavior if the high-pedal disable switch is stuck? Any other ideas? Controller bad? Curtis manual had troubleshooting guide, but doesn't cover HPD feature well at all. Thanks!