1985 gmc k1500 wipers only move at 1 slow spped, interminttent doesnt work at all. How fast is fast and why is fast not working?

Why are you 'sending voltage' ?? IIRC, that system uses a switched ground. In that case, you're sending voltage through a ground circuit!! The system receives power always with key on.

You may have destroyed the pulse module sending power down those circuits.

Here's the basic layout. There are three brushes in the motor. A common which passes current for both speeds. Then there is a slow speed brush and a high speed brush. The switch chooses which speed and ultimately which brush receives current. The motor will then operate at that speed. Added to the mix is a parking circuit and possible a pulse wiper circuit. These circuits are usually housed within the wiper motor case itself. Your truck has a separate box module for that pulse circuitry. The wiring from the steering column should plug directly into the pulse module. The motor harness also plugs into the module.

IIRC, you can disconnect both harnesses from the module and plug them together. No pulse operation, but you'll have basic two speed wipers.

What you need to do is look for power at the motor with the key turned on and the wiper switch turned off. It should be the white wire. Testing at the motor, and the switch turned to 'Lo', the grey wire should show ground. With the wiper switch turned to 'Hi', the purple wire should show ground. You can test the motor by applying ground at those terminals one at a time.

At the steering column wiring, there should be a good ground to the black wire.

BTW - thanks for the crappy rating. No rating is better than a bad rating. I answered your original questions. Why the bad rating?




Why are you 'sending voltage' ?? IIRC, that system uses a switched ground. In that case, you're sending voltage through a ground circuit!! The system receives power always with key on.

You may have destroyed the pulse module sending power down those circuits.

Here's the basic layout. There are three brushes in the motor. A common which passes current for both speeds. Then there is a slow speed brush and a high speed brush. The switch chooses which speed and ultimately which brush receives current. The motor will then operate at that speed. Added to the mix is a parking circuit and possible a pulse wiper circuit. These circuits are usually housed within the wiper motor case itself. Your truck has a separate box module for that pulse circuitry. The wiring from the steering column should plug directly into the pulse module. The motor harness also plugs into the module.

IIRC, you can disconnect both harnesses from the module and plug them together. No pulse operation, but you'll have basic two speed wipers.

What you need to do is look for power at the motor with the key turned on and the wiper switch turned off. It should be the white wire. Testing at the motor, and the switch turned to 'Lo', the grey wire should show ground. With the wiper switch turned to 'Hi', the purple wire should show ground. You can test the motor by applying ground at those terminals one at a time.

At the steering column wiring, there should be a good ground to the black wire.

BTW - thanks for the crappy rating. No rating is better than a bad rating. I answered your original questions. Why the bad rating?