Earthing education.

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midget
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Earthing education.

Postby midget » Thu Jan 10, 2019 7:51 pm

I admit to being an electrical dummy, so must risk appearing stupid but cannot get my head around a problem that is the last step of re looming my van. Discovered that my wiper motor was seized so fitted an ESM replacement.
Although this works normally, it will not self park when power is disconnected. I have read up on here and checked the wiring, and all should be well. My problem is what does the black wire connect to when diagram states that it is connected to the "control box" ?
I assume this means the regulator when using a dynamo, but I have done away with this as I have an alternator, and fitted 2 fuse boxes in its place. This was done many moons ago so all is well with this set up.

I have tried to trace the black which is supposed to be connected here but cannot see any black returning to this area?
Question is where should the returning black be connected to with this set up please?

Supplementary question is ...what is the difference in earthing at any point on the chassis or at the "control box"?
John

simmitc
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Re: Earthing education.

Postby simmitc » Thu Jan 10, 2019 8:46 pm

The "E" terminal on the control box connects to earth, ie the body, and any other component that is connected to the body will also have the same earth connection, so you do not need to run a wire back to your now missing control box; just take the wire to the body.

The self parking problem will be caused by the cap switch on the wiper motor and no path to earth. If the problem persists after earthing your black wire then check under the round cover - when you transferred the gear wheel, did you attach the copper upright contact correctly? If yes, then try rotating the cap and see if the motor moves.

Note that the wiper circuit is unusual in that the switching is on the earth side with the non-earth side being permanently connected to the motor.

midget
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Re: Earthing education.

Postby midget » Fri Jan 11, 2019 7:49 am

Thank for demystifying the earth question--so why do instructions and diagrams insist on "Taking an earth back to control box"?

I will investigate the motor cap which,as you say, had to be relieved of its drive wheel and cable link arm for exchange. I confess that I did not notice any specific upright earthing contact when I fitted it. I did pack the area well with grease which may be a cause?

Much obliged.
John

midget
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Re: Earthing education.

Postby midget » Fri Jan 11, 2019 7:10 pm

Here is the relevant section pictured earlier today. Can't see any earthing contact--am I missing something please?


Image
John

biomed32uk
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Re: Earthing education.

Postby biomed32uk » Fri Jan 11, 2019 10:29 pm

You are missing the contact finger and c clip that holds it on, it makes contact with the lid, you can see the mark where it runs around. This is what sets the park position of the motor.


You can just see it in this picture
wiper motor contact.JPG
wiper motor contact.JPG (16.54 KiB) Viewed 249 times

midget
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Re: Earthing education.

Postby midget » Sat Jan 12, 2019 9:22 am

Ah yes, I see it. I assume this is soldered to the wiper casing? If so it is missing from the new one.
I will contact the supplier.

Thanks
John

biomed32uk
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Re: Earthing education.

Postby biomed32uk » Sat Jan 12, 2019 10:02 am

No it's not soldered on, fits over the end of the post and is then retained by the C clip, which also keeps the drive to the rack retained as well.

It makes contact with the brass pad in the cap, where the wire goes to.

The wiper motor works by switching the earth, that contact in the cap is also earthed. You can see there is a piece missing, 8 to 10 o'clock in your picture.

This part is just going round when the wipers are running, when you switch off it could be anywhere, if it is on the brass bit the motor will continue to run until it finds the missing segment, loses contact with earth and the motor stops. This is the parking position, so you can tweak it by rotating the cap.

midget
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Re: Earthing education.

Postby midget » Sat Jan 12, 2019 1:58 pm

Yes, I understand the principle but do not remember removing the earthing finger when refitting the drive wheel and arm.
I assume that it would have to been in my possession and not supplied by seller? The old (returned for exchange) motor parked as usual.
I obviously removed and refitted drive gear so must have mislaid the finger.

Thanks for help.
John


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