'71 K20 Windshield Washer Problem

[flyingtim01]

Hi Guys,

Got an issue that I was battling a year ago and just gave up on it. The wiper motor works, but when the wipers are running, so is the washer pump, regardless of whether I've pushed in the switch or not. I figured the switch was no good, so I ordered a new one from LMC, and it does the same thing. I finally just disconnected the hose from the reservoir. I don't drive the truck much anyway, so I can use the wipers sparingly.

I'd like to try and get it ironed out. I have the stock motor and pump setup, not an aftermarket washer pump. Any help you guys can provide would be great. I imagine this is a ground issue, I know that the motor has 12V all the time and relies on grounding for the different speeds, but I'm not quite sure how the washer pump works.

[panhandler62]

Someone should verify but... I think 12v is supplied to the pump from the wiper motor when the motor is on and that the push button incorporated in the wiper switch provides the ground.

[flyingtim01]

Okay, so if the switch provides the ground, that must mean the switch is faulty, if it's grounding the pump circuit, right?

[panhandler62]

Or.. (unless I am wrong about the circuit) the pump might be shorted to ground somewhere.

There are 2 leads on the pump. 1 of them is coming right from the wiper motor. the other runs back to the switch. If you pull the one that goes to the switch (should be dark blue) you should be able to run the wipers without the pump running.

If that is true then measure from the wire end (when disconnected) to ground with a multimeter and if it is low impedance then the wire is compromised.

If the wire checks out or if the pump still runs with the wipers on when the wire is disconnected; it's likely that the pump itself is shorted to ground.

[flyingtim01]

Okay, thanks for the leads to chase Panhandler62. I'll take a look and see what wires I have going where and start to chase some gremlins.