Put the wipers on steady slow or fast, then instead of measuring the voltage at the connector, measure the voltage on the wiper motor case. The voltmeter or test light should be grounded to the engine or battery negative post.
When you find voltage on the case, push on the mounting plate and the motor will start to run. The plate is mounted on three rubber isolators to dampen vibration. To get a ground, there is a brass strip riveted to the plate by the lower left bolt. A ring is burned around that strip under the bolt head. Do not bother trying to clean it up. That rarely lasts. Instead, bolt a new ground wire to the mounting plate and bolt the other end to the body sheet metal.
One other note. There must be twelve volts on two terminals at the motor. One from the wiper switch, and one whenever the ignition switch is turned on for the "park" circuit to keep the motor running after the wiper switch is turned off. If one of those voltages is missing, suspect a blown fuse due to your old motor was shorted. It was quite common for one of the contacts on the rotary switch in the motor gear train to overheat. It would melt into the plastic gear when the motor was turned off. The next time the motor started to run, that contact would get stretched and bent up until it touched the metal cover. That popped the fuse. Chances are your old motor is okay if you have the ground problem. It is not likely to develop both problems at the same time.
Wednesday, March 3rd, 2010 AT 1:10 PM