Why Wipers don't work on high?

Answer 1

Several possibilities are that:

1 the switch is bad on the high position.

2. There is a problem with the high speed wire from the switch to the motor.

3. The wiring inside of the wiper motor for the high speed is bad.

The way 2 speed wiper motors work is there are separate windings inside the motor for low and high speeds. Usually 2 wires come out of the motor for low and high and the common ground through the wiper motor body to the chassis of the vehicle. You apply 12v to one wire and get low and 12v to the other one for high speed.