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Wiper won't stop. Any suggestions?
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pastellgreen
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PostPosted: Sun Jul 03, 2022 2:02 pm    Post subject: Wiper won't stop. Any suggestions? Reply with quote

1) I already read other threads concerning this
2) Already had a look into the shop manual

Car: Absolute original VW1200 from 1961, low mileage. Comes from Portugal, almost never seen rain. Wiper assembly like new, also the motor. Switch is the one year only with bellow at the backside.

Old thing: you turn the switch off, the wiper tend to park but anyhow they go further and do not stop.

What I've done:
Disassembled the wiper assembly. Had a look on the motor and contacts, all is in stock condition. Contacts should have 0,6 - 0,8mm distance. Took a feeler gauge and measured a distance from 0,8 at the park position and 0,6 at the running position. Regreased the lobe pin although it was going nice in and out already. Cleaned the contacts and the contact area. Checked the passage of both contact postitions, resistance was both at 0,2.
Reinstalled the assembly. Wipers parked two or three times as they should, afterwards the problem continues, they do not stop any more.
Checked the ground from 31b at the motor to the body and also from the switch to the body: Perfect. No further ideas. Such a pitty, as the whole car is so perfect and original, all things are in working order.

1) Please: Anyone?
2) Could it be the switch?
3) There is a little internal wire from 54 to one of the brushes. If its insulation is defective, would it cause this kind of problem?
4) When there is no idea or way to solve this, is it possible to change the stock wiring to go on without a park position but a guaranteed way to stop the wiper?


Last edited by pastellgreen on Sun Jul 03, 2022 11:05 pm; edited 1 time in total
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richparker
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PostPosted: Sun Jul 03, 2022 3:28 pm    Post subject: Re: Wiper won't stop. Any suggestions? Reply with quote

Years ago I have a ‘68 Westy that did the same thing. In my case the switch was wired wrong. I fixed that and they worked as they should.
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EVfun
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PostPosted: Sun Jul 03, 2022 4:18 pm    Post subject: Re: Wiper won't stop. Any suggestions? Reply with quote

Measure the resistance of the switch terminal 31b to ground with the switch in the off position. The switch may be the problem, if isn't the contacts in the wiper motor. Your problem is that the plug braking of the motor, to cause a rapid stop at park, is not working. The motor should see a short across the armature when the switch is off and the wipers are near the bottom.

It is not a pitty -- it is just a bad connection! Let's find it and fix it. Here is a picture of the wiper and switch terminals and functions, courtesy of GS guy

Image may have been reduced in size. Click image to view fullscreen.

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pastellgreen
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PostPosted: Sun Jul 03, 2022 11:12 pm    Post subject: Re: Wiper won't stop. Any suggestions? Reply with quote

Thank you for your support!
pastellgreen wrote:
Checked the ground from 31b at the motor to the body and also from the switch to the body: Perfect.

Already done this. The wiring was in stock condition (the car was nearly untouched) and correct. I assume the issue of question (3) shouldn't lead to this parking position, more to a short that the motor wouldn't run any more.
I don't understand, why it is important to have a contact distance from 0,6 to 0,8. For my understanding, the larger the gap, the safer its insulation. Would it be a bad idea to go above 0,8mm contact gap?
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EVfun
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PostPosted: Mon Jul 04, 2022 6:54 am    Post subject: Re: Wiper won't stop. Any suggestions? Reply with quote

With the wiper motor stopped in what should be the parked position, switch off, measure the resistance between 31b and 54d at the switch. It is a full system check of the wires and cam function check inside the wiper motor.

You certainly don't need to go looking for more contact clearance inside the wiper motor, if anything you need less. The idea is to short the motor windings out when the wiper motor needs to stop. This is "plug braking" and it causes an electric motor to stop very quickly. They need to be shorted for enough degrees of rotation to do the job. Oh, you are testing this function with the wipers on the windshield, right?

Looking at the picture of what is happening from GS guy you can see that motor terminal 54 always has power. Because of this when you turn off the wipers they do not initially stop. The cam is shown in the park position so when they are running right after you turn off the switch the cam is facing away from the moving contact and power goes from 54 through the contacts and to the motor armature (M in the image.) When the wipers reach the bottom the cam has rotated to the position shown and now the armature is disconnected from power but shorted to ground through the contacts, the wire back to the switch, through the switch contacts, and back to ground through the switch body to the dashboard sheet metal.

What are you testing your connections with? You say they are "Perfect" but there is so such a thing. Given a good enough meter I can read resistance in every connection and every length of wire. A beeping continuity meter is not an adequate test. We need to measure actual ohms, down to the tenths of an ohm. This is especially true in a 6 volt car.
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pastellgreen
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PostPosted: Mon Jul 04, 2022 1:35 pm    Post subject: Re: Wiper won't stop. Any suggestions? Reply with quote

Ok, that advice took me to do more measuring. The ohms always have been around 002, so I wasn't aware there could be something wrong.
But then I came to the idea to disconnect the wiring from the switch and to test the 31b terminal to body. There was no reliable ground, it depended on how I was pushing the terminal...
Pulled the switch out of the car and checked it. When switched off, the ground was still not reliable. Fortunately, I had another of these one year only switches. Before installing into the car, I measured it and the ground at 31b was perfect.
It was too late to start the car, tomorrow on the way to work, I will see if this was the solution. I like to test it with engine on (generator produces more power) and a wet windshield.
I disassembled the old switch and found the contacts inside perfectly clean. That was what I expected for this low mileage car but does not explain, why it was not reliable. I will try to find a solution to replace the rivets by screws and reassemble it, perhaps it will work again. These switches are hard to find with still soft and working bellows.
Found today a NOS contact block for the wiper motor in the internet and ordered it. Perhaps I won't need it now, but will keep it for the future.
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pastellgreen
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PostPosted: Tue Jul 05, 2022 1:37 am    Post subject: Re: Wiper won't stop. Any suggestions? Reply with quote

After test drive this morning it can be stated, the wipers do park again!
Thank you very much for your support!
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