I have a 1970 roadster and have been working on getting the wipers working. Fuses were blowing and found the the override switch was dirty so cleaning it eliminated the resistance in the circuit and now the fuse does not blow and the switch functions properly.

Now the problem is that the wipers will not turn off when the ignition is on (both with and without the car running). The speeds change as they should when operating the wiper switch but going to off does nothing. The wipers continue to run on low. When I shut the ignition off, the wipers shut off and park as they should. When I turn the car on again, the wipers start again.

I unplugged the three wire connector and connect two continuity testers, one to the green and the other to the blue wire. I set them up to check for continuity to ground. With the ignition on, when I operate the switch they indicate short to ground as then should when running the switch from off to low to high and back down (green and blue short to ground on low, blue only short to ground on high, and both green and blue open when switch is set to off). So this all looks like it is switching the wires properly per what I have read.

I plugged the connector to to the motor and again check the green and blue for continuity to ground while it is plugged in. The green wire shows connection to ground as it should in low and the blue and green show connection to ground at high. When I move the switch back down to low I get green to ground and blue and ground and the motor goes to low. When I move the switch to off the green moves off ground but the blue does not thus the wipers continue to run and not park.

Any thoughts on where to look? I look throughout the forum and did not see this one.

 

Verify that the dash wiper switch is grounded.
Normally grounds via the center cluster.
Easy to test/verify - simply run a known ground wire (straight from the battery if you like) to the center gauge cluster and and see if the completes the wiper park circuit.
Also, verify that the wiper motor is grounded.
Normally via the black harness wire that runs across the firewall - grounds the wiper motor, blower motor, then terminates at the starter mount bolt. (of course you can test by simply running a temp ground to the case).

 

If the switch wasn't grounded the wipers wouldn't run at all.

 

EK,

I would also try bench testing the motor in your car.
Just unplug the three wire connector on the back of the motor, run a 12V power wire to the middle connector, then try to run through the sequence: Ground one prong -> ground both sides -> then ground the other side by itself -> and back

Note: try not to remove the ground while the wiper is on high speed because that can lead to motor run on

 

Thanks for the feedback. I tested the motor and switch ground using direct connections to ground and that did not change the outcome. I pulled the switch and did a continuity test on it and it appears to be good. I'm struggling understanding the interaction between the switch and the relay. Can anyone explain how this works? What signals are going from the switch to the relay on which wires and what is the relay doing in response to the signals. Thanks.

 

When you turn the ignition on, you get 12v to the wiper motor. When you move the wiper switch to "low", the switch grounds two wires to the console ground where it's mounted. When you slide the switch to "high", it only grounds one of those two wires to the same ground. The wiper switch only provides ground to the proper wires. The third wire to the switch is grounded when you push to "wash" to activate the washer pump. There is no relay in the actual wiper switch operation. There are other functions that will disable the wipers when the door isn't open, and you have the override switch under the dash to stop the wipers, but you said your problem was that they wouldn't shut off. The wiper motor has to be getting a ground when it shouldn't. If you unplug the wiper switch plug, do the wipers still come on when you turn on the ignition? If so, the switch isn't causing your problem.

 

According the the diagram in Willcox there is a relay to is located under the forward center console. I'm trying to understand it's purpose and how it works with the switch to signal the wiper motor. It appears to control the green wire circuit. If attached the diagram I am referring to.

 

The relay is what actually switches the ground for low speed/off.
Edit: Sorry, that's poorly worded.

When you move your switch between low and off do you hear a clicking from the relay (under the console)?

Edit: Here is what is happening:
First the switch is off (and on low speed), the black/white wire is grounded and the relay is passing continuity between the green wire and the black wire (constant ground)
When the ignition is on and the switch is on low speed then the relay is energized and pulls the contact to pass continuity between the greed wire and the black/white wire from the switch.
When the switch is on high speed the switch drops the ground from the black/white wire and (because the relay is passing continuity) the motor loses ground on that connector.

 

If your switch is not grounding the dark blue wire (shown on the diagram) when in the off position and your wiper motor connector is seeing a ground on the blue wire, then there is a short somewhere in your wiring.

 

Thanks. That is what I needed to know! When I unplug the connector from the wiper motor and test continuity to ground on the green and blue wires, they follow the pattern that they should. When I plug it into the motor, I start the wiper by moving the wiper switch and the wiper motor turns on and goes from low to high as it should. When I move the switch to off, the motor keeps running (does not park). It appears I may have a short on the blue terminal to ground inside the motor. I have something to check tonight when I get home from work.

 

That explanation from you that you start your wipers then they won't turn off makes a difference. Your first statement of wipers on anytime key is on made me think as soon as you turned the ignition on the wipers began on their own. It sounds like your problem is in the park switch.

Take a look at this old post with a resolution to the same problem you have:
https://www.corvetteforum.com/forums...on-t-park.html

 

Well I ran some tests last night on the car. I ran the motor test and it all checked out. The motor moved through the speeds and parked when I opened up the ground connection to the blue wire. So that is not the problem. I did a continuity / resistance check on the blue wire from the dash/wiper switch connector to the motor connector and while it is not shorted, it reads about 350 ohms. Note that when connected to the switch and operated the resistance goes to almost zero (again this is measured to ground) So I'm assuming I have a leak to ground somewhere in the circuit and it is enough to cause the motor to not see enough resistance to park the motor. So now I start the search. It will probably be a winter project. Don't drive the car in the rain so I don't need the wipers anyway. Just want to get them to work. Thanks for all the input. If anyone has any suggestions on where to look that would be helpful. I'm thinking I will look at the wiper relay when I can get to it. Seems like a crazy place for the GM to put that relay!