Most likely the ground is missing. Start by testing for voltage on the motor's housing. Put the meter's negative probe or the test light's clip lead on any ground other than the plate the motor is bolted to. Wiper motors are usually mounted to a metal plate that is mounted with rubber isolators to dampen vibration. There is a brass strip riveted to the plate, and run under one of the bolt heads. That strip arcs away under the bolt head. Often the motor will run intermittently, and when you push on it.
Do not bother trying to fix that brass strip. Just find a place where you can attach a ten gauge jumper wire to the plate or motor, and the other end to a paint-free point on the body.
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Thursday, December 14th, 2017 AT 2:41 PM