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Really stupid question
Posted by: flat_six ()
Date: February 20, 2021 03:06PM

I’ve been around Corvairs for 50 years and can’t figure this out.

Wiper motor. When I just set it in the trunk, plug it in to the car and switch it on, it runs of course. As soon as I turn off the switch on the dash, it stops. In any position.

When I attach it to the wiper linkage, install it in the car, and turn it on, let it operate, then turn it off, it waits for the wipers to return to the park position before stopping.

So how does it know when the wipers are parked?? The only difference is mechanically attaching the motor to the linkage and to the firewall.

Two different motors did this.

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Re: Really stupid question
Posted by: MattNall ()
Date: February 20, 2021 03:34PM

The linkage / arms /wiper slow it when you shut it off. Without them it just glides thru the dead area.

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Re: Really stupid question
Posted by: cnicol ()
Date: February 20, 2021 03:37PM

The motor is controlled by grounding. The "hot" side is ON all the time.

When you turn the switch, you're connecting the ground to the slow or fast winding.

When you shut it off and it's not parked, there's a rotating contact disc that's all brass except for one portion that just plastic.

A spring-loaded contact bears on that disc and provides ground *through the wiper housing that's screwed to the body*. The disc rotates with the wiper arms until the contact reaches the missing segment and at that point there's no longer any ground to the motor and it stops.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: Really stupid question
Posted by: Wagon Master ()
Date: February 20, 2021 03:42PM

Park cam.
Service Manuals are your friend.

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Re: Really stupid question
Posted by: oldqmguy ()
Date: February 20, 2021 04:10PM

Craig nailed it!

If the motor is NOT mounted to the frame the Parking Switch has no ground so it can't keep the motor running!

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Re: Really stupid question
Posted by: 66vairman ()
Date: February 20, 2021 04:25PM

Yup the "PARK POSITION" function.

That bit of engineering is why the power goes to the wiper plug from the fuse box. and ALL the wiper switch functions provide a ground.

So if the wiper motor housing is NOT properly grounded the motor stops ASAP when the wiper switch is turned off. The PARK points keep the motor grounded until cam gear that works the wiper linkage arm is in the park position (always make sure this is the case BEFORE installing wiper arms.

On my 66 LM wiper motor the PARK switch is in the wiper motor gearbox. Unlike what craig observed, mine is a set of points that are opened/closed via an inner cam that is part of the reduction gear (nylon). BTW - a few folks have damaged the inner PARK points by trying to remove the washer mechanism cam (newer units use a different cam). If you yank on that shaft with too much force then things inside the gearbox get bent!!!

The gear box is riveted together, but it can be dismantled and repaired/lubed.

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Re: Really stupid question
Posted by: cnicol ()
Date: February 20, 2021 05:30PM

66Vairman wrote: "On my 66 LM wiper motor the PARK switch is in the wiper motor gearbox. Unlike what craig observed, mine is a set of points that are opened/closed via an inner cam that is part of the reduction gear (nylon)."

Craig replies: Wow, that's interesting. With all the '66 Corvairs I've owned, it would seem that either I've never opened-up one of their wiper motors or I'm remembering the park mech from a different vehicle I've worked on. At any rate, same concept. Thanks for the education.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: Really stupid question
Posted by: flat_six ()
Date: February 20, 2021 08:17PM

That explains it! The park points must be inside the gear housing.

Yes, installing the motor causes the upper screw to bond the copper ground strap with the body, enabling the park points. Pretty elegant engineering!

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