72 Cutlass Supreme windshield wipers only work on one speed
May 28th, 2018, 09:52 AM
#1
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Join Date: Oct 2015
Location: Atl Ga
Posts: 89
72 Cutlass Supreme windshield wipers only work on one speed
My windshield wipers in my 72 cutlass only operate on the highest wiper speed and not the lower one. Does anyone know the reason for this? I知 assuming it may be the wiper switch but I知 not sure.
May 28th, 2018, 11:13 AM
#2
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 47,310
Your Chassis Service Manual has a whole section on troubleshooting this problem. The round GM wiper motor uses a shunt winding design to get low speed. The shunt winding is wound in the opposite direction from the high speed winding. To get high speed, only the high speed winding is powered. To get low speed, BOTH the high speed and low speed windings are powered. Since the shunt winding is in the opposite direction, it partly cancels out the magnetic force of the high speed winding, which then gives you low speed.
Anything that prevents the shunt winding from being powered can cause this. It could be the switch, the wiring to the motor, the connectors between the switch and the motor, or the motor itself. This is why you need to follow the troubleshooting procedure in the CSM to avoid replacing parts that aren't bad.
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