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Discussion Starter #1
Has anyone disassembled it without breaking the tabs that hold the back panel to the assembly? Thanks.
 

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Nearly no broken tabs. You'll usually break at least 1 of the larger clips. I think it's essentially impossible to get it apart with no damage. The smaller ones are easier to take apart. It will still go back together fine with a couple of broken clips. You need a few tiny flat blade screw drivers used at the same time. It's a real PITA.

Good luck,
-Rob
 

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I usually use a cable tie to keep them closed. Be careful if you take out the actual motor to put it back in the same orientation. Otherwise it runs in reverse and the motor never stops.
 

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yeah, I had troubles on a car with the thing always comming apart because there was not enough keeping the back plate on.
 

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put it close to the front of a blow heater or hair dryer for a minute or so and this will soften the plastic a bit as we all know due to the age it hardens and is brittle, but warmed up if should come out easier as its soft again, but as above if any break a cable tie will hold it together
 

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Discussion Starter #6
I finally got round to opening it and managed to pry it open with the help of another pair of hands.

Several things were wrong with the wiper that cause it not to work:

1) Stiff cam. The white plastic cam was stiff (see below) and didn't rotate smoothly within the holder.

2) Misaligned rod guide. The holder/guide of the main wiper shaft was misaligned with the rod and made it hard for the rod to rotate.

3) The motor slows down and stops before the 5 wipes. I found a 1cm square piece of "resistor" of about 20ohms, wedged in line with the motor power supply (see arrow in picture)



If the resistor is shorted, the wiper turns powerfully. Too powerfully, to my mind. It's not the diode tho - that seems to be embedded into the assembly.

Does anyone know the function of this resistor? I'm going to short it out if there's no real function for it.
 

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That resistor....

is called a PTC resistor.
Positive Temp Coefficent.
(The resistor in-between cyls 2 & 3 on the intake manifold is a NTC.
Negative Temp Coefficent. As it heats up, the resistance value goes DOWN.)

Resistance goes up as it heats up.
Ideally,.....
PTC is there to go high in value should the wiper assembly be stalled or ceased or very stiff to rotate. If the motor was to be physically loaded down above the rated torque value the motor would draw higher current that usual and heat up the PTC. Resistance value would increase quickly to reduce the chance of a winding burning up or shorting internally.
Good idea in theory....... but as the motors age, and the wiper assemblies get a little stiffer, the motors just cannot produce the rotational force per unit of current as they did when new. The windings change in value (ie: they begin to breakdown and short) and they become the higher current load and thus heat up the PTC. PTC gets so hot as to reduce the voltage at the motor and so, ends the rotation until the PTC cools down.

Both my headlight wiper assy's suffer this sadly.
 

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Rodentmaster said:
That resistor....

is called a PTC resistor.
Positive Temp Coefficent.
(The resistor in-between cyls 2 & 3 on the intake manifold is a NTC.
Negative Temp Coefficent. As it heats up, the resistance value goes DOWN.)

Resistance goes up as it heats up.
Ideally,.....
PTC is there to go high in value should the wiper assembly be stalled or ceased or very stiff to rotate. If the motor was to be physically loaded down above the rated torque value the motor would draw higher current that usual and heat up the PTC. Resistance value would increase quickly to reduce the chance of a winding burning up or shorting internally.
Good idea in theory....... but as the motors age, and the wiper assemblies get a little stiffer, the motors just cannot produce the rotational force per unit of current as they did when new. The windings change in value (ie: they begin to breakdown and short) and they become the higher current load and thus heat up the PTC. PTC gets so hot as to reduce the voltage at the motor and so, ends the rotation until the PTC cools down.

Both my headlight wiper assy's suffer this sadly.
Ah... In other words, bypass it, and your wipers'll probably work well, but if you try and use 'em when they're iced to the glass or buried under snow - you'll burn the motors out.

Thanks for that - that explains why my RH one sometimes stops _near_ the rest, but mainly on it, whilst the LH one obviously isn't totally seized, because it's moved a bit but not much.

A damn good clean up and regrease has worked nicely on windscreen wiper motors for me in the past - wonder whether it will here, too? I reckon I'll spray a shedload of electrical contact cleaner into the actual motor, but otherwise leave that untouched. Just do the mechanical linkages.
 

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Well, I guess....

I'm not saying don't use the spray,......but I tend think it may give you more issues. I don't think the motor will get any better for you unfortunately.

All d.c. motors use carbon brushes against copper contacts (or slip rings in the alternators). With use comes friction and wear 'n tear. The carbon brushes emit a fine carbon powder, the copper contacts shed copper dust.......if you were to add the spray,...it can just spread it around where it 's not meant to be. That copper and carbon powder can find it's way into bearings and other friction points not meant to be contaminted with such material which can promote more agressive wear etc....


Please, I'm no purist and I'm not tryinig to be a P.I.T.A. here but I have seen some effects of 'cleaner' spray or similar in automation motors and other broadcast machinery in the name of lazy maintenance from the overnight goons and the results generally were not in our favour.

When I rebuilt my alternator, I soaked the windings and diode assy in isopropynol, then turps, then a quick rinse in very hot lightly soapy water. The gunk that came out was amazing and to see the glitter of copper in the black sludge.


I'm still trying to find an alternate motor to put in the assy's, problem is the phyiscal layout of the contacts inside.


Good luck
 

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I like that thread.....


especially this bit......

The motor (Bosch part number 1-397-220-056) is available in the UK from:

ELLIS COMPONENTS
Stonebroom Ind. Est.
Stonebroom
Alfreton
Derbyshire
DE55 6LQ


Tel: 01773 873151
[email protected]






That has made my Christmas!
Thanks Matthew.
 

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Be aware that the polarity of the motor matters in the housing. If you put it back in the wrong way, it will happily work, the wiper will wipe but it will never park. Reason is there's a cam cog that lifts a switch to park the wiper. If the motor is turning backwards, the cam cannot lift the switch.
 
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