'67 vs '72 Wiper Motor

[1972RedNeck]

Can anyone tell me the differences between '64 - '68 and the later wiper motors? Is it just the 3 vs 4 terminals? Or are there other differences? Will they interchange?

[Jrainman]

I am not sure what year the change , of what is called self park another words the wipers will return to lowest position automaticly when the switch is turned off ,the early motors would park themselves in any position on the glass when the switch is turned off. and also as you stated 2 spd and 3spd motors

[ray_mcavoy]

As far as I know, all of the 1967 through 1972 GM truck wiper motors are interchangeable. All of them in this year range should have the self-parking feature. If you come across one that doesn't self park it's likely due to a bad parking switch (located inside the motor's gearbox assembly) or a bad ground (typically a copper/brass strap connected across one of the rubber mounting grommets).

The 3 and 4 terminal motors are both 2-speed with a washer. I've never seen a 3-speed wiper in any of these trucks. The 4th terminal (on motors that have it) is simply a second +12V power terminal (it's connected directly to the terminal right beside it). That 4th terminal connects to a short jumper wire that feeds power over to the washer solenoid. On the 3-terminal motors without that 2nd power terminal, the wiring harness is constructed such that the power feed wire goes to the wiper motor and then branches off to feed the washer solenoid. The remaining two terminals (on either style of motor) are both connected to the dash switch that grounds one of them for high speed or grounds both of them for low speed.