Just take a wire and run it from the switch housing to the mounting plate of the wiper motor. This iwll tie them together with the same ground.. Now, your switch should function properly… It sounds like they are not sharing the same ground.. They MUST in order to work because the the switch must ground the motor to make it work..

Run a jumper wire fro the switch housing to your wiper motor mount plate.. this should fix your issues

Correct.. the switch MUST be grounded or you can not complete the circuit. The purple wire is the 12V Feed.. the switch completes the the circuit based on which speed you are running. So the switch MUST be ground to the SAME ground as the motor or it will not turn on.. Very important IF bench testing.. you have to jumper the switch to the motor..…[Read more]

With 2 speed wiper , the single red goes on the outside of the wiper motor.. It is the switch for the speeds.. purple in the middle (power feed from the switch)

Be careful… The ground is connected via the switch itself, without the switch being grounded, the motor will not turn on.