<VV> GM Wiper Motor Issue - Possible Corvair

[Grant Young]

I turned on the wipers on my '72 Caddy with 3-speeds, mist and  wash only to discover they would not turn off. I checked and disassembled the interior switch and it seems fine. Unplugging it does not turn them off. The only way to stop them is to unplug the two-wire plug to the motor, but they do not go to the park position. Wondering if this is a relay issue (if so, and where it might be if not in the motor assembly) and how it might be repaired. My guess is that something isn't getting grounded or opened when it should. Replacement rebuilds are over $150, so I would like to take a shot at it myself if possible. A private reply if fine if the Corvair motor is significantly different. Thanks,
Grant