Wiper motor

[JWalter 64]

Can anyone tell me what the difference between a 3 terminal and a 4 terminal is on a two speed wiper motor?

[gabbin]

I think the difference is if you have the washer set up, that would be for the extra terminal.

[ray_mcavoy]

The 4th terminal (when present) is located right beside (and internally connected to) the wiper motor's power feed terminal. The 4th terminal is used to feed power on to the washer.

There were also some 3-terminal wiper motors that were equipped with a washer. They used a slightly different wiring harness where the power feed wires to the wiper motor & washer were joined together at the plug to form a daisy chain type power feed connection.

So as long as you are dealing with motors that have compatible style gearboxes, a 4-terminal motor can be used to directly replace a 3-terminal motor without any changes to the wiring (just leave the 4th terminal unused).

Going the other way around (using a 3-terminal motor to replace a 4-terminal motor) is also possible if you use a piggy back adapter to connect the 2 power feed wires together ... something like this:

[aerotruk63]

In the GM parts book it indicates one part number for a 2 speed and a different part number for two speed with washer.