Three position switch (off/slow/fast) not working. Bought a new switch and have same problem. The SWITCH OFF position gives very slow wiper movement. The SWITCH SLOW and SWITCH FAST position work OK. The only way I can turn off wipers is to high-center the switch between positions. But it won’t stay high-centered very long. Is this a wiper motor problem? Thanks for any help.
You probably got a bad wiper switch.
After all, this a dumb circuit.
There’s no computers/modules controlling the wiper motor.
It’s all controlled thru the switch.
Sounds like you need one of these:
I’m guessing the parking switch in the wiper motor assembly itself is bad. Replace the wiper motor.
My 1978 Oldsmobile had two speed wipers and the switch completed the circuit to the chassis ground. When the.switch was on high, the path to geound was direct. I’m low position the motor was connected in series with a resistor to ground. In the off position, there was no connection to ground. A wiring diagram will show you if your truck has this set-up. If it does, I,would suspect the switch.
I believe it’s in the motor. The sensor that allows the motor to continue running until the wipers are parked is faulty or not adjusted right, so it never senses that the wipers are parked. With this age vehicle I’d visit my local auto parts recycler, but a rebuilt one is less than $50.