My wipers have me perplexed on my 72 coupe. Until recently they had worked normally. Now when I vacuum override the wiper door to open, the wipers come on low speed despite the switch in the "off" position. they will go to "high" when switched to "high" but remain on even if switched to off. They will shut off to "park" position when ignition key shut off and remain off once wiper door closed. When turning wipers on with switch, they come on normally but will remain on as described above. Where do I start? Switch?

My guess is the motor itself. There are contacts inside that keep the motor running after it is shut off with the dash switch, so it can park. The safety interlock on the wiper door ( on the firewall) connects power to the motor, it starts running again because the cancel function is bad in the motor.

My 89 Chevy wagon did this, you had to turn the key off to get them to park.

My 2 cents