W124 Headlamp wipers, what have I done wrong?

roadhog

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The near side headlamp wiper on my car stopped working for the second time since I've had the car. The first time it was the shaft seizing in the tube (a common fault I believe) and I fixed it with a good clean and lube. So this time I thought I was in for another one of those. Wrong.
The shaft turned freely so I emptied the gubbins out, cleaned them and reassembled. Now the wiper duly works but in the wrong direction. :confused:
I've turned the motor around but that only results in the mechanism stopping after one turn because one of the little cogs is obviously going the wrong way round and gets jammed behind the contacts it's supposed to open/close.
I swear it's all back together the way it came out but for the life of me I can't work out why it's going the wrong way round. Help. :(
 

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Reversing the carbon brush wires will reverse it or the live in
 
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roadhog

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Thanks Malcolm but the motor is not really designed to be opened (and successfully put back together by someone as hamfisted as me). The easiest way to reverse the motor is to fit it the other way round (it's symmetrical) but that just results in the mechanism jamming up after one rotation.

Anyhow, I think I've sussed it. Predictably it was me who caused the problem. In the picture below you'll see a green disc. It's the back of one of the sprockets and needs rotating 180 degrees to work in the correct sense.
Well that's the theory, I'll know whether I'm right later.
 

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television

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You could have given us the way to reverse them :D:D

Anyone with a 124 or 126 and they headlamp wipers do not park correctly, it is because the switch was held for to short a period and did not let the parking set. Holding the wash switch for a little longer they will park,,I have a mod for this somewhere so that they will park all the time
 

SilverSaloon

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i've done this a few times now.

your problem is probably that you've reconnected the cogs in the wrong position or the "rack" is initialised at the wrong end. often the wiper will start to wipe again before cutting out if the rack is not at the end (ie in the middle). if its at the opposite end, the wiper will rotate the wrong way.

i would recommend taking it apart again and refitting and try and visulise how it should spin to ensure its the right way. also you could put 12v direct to it to test before refitting.
 
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roadhog

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Holding the wash switch for a little longer they will park,,I have a mod for this somewhere so that they will park all the time

I'd like a look at that please Malcolm, it just looks soooo unsightly when the wipers aren't parked properly. :)

i've done this a few times now.

your problem is probably that you've reconnected the cogs in the wrong position or the "rack" is initialised at the wrong end. often the wiper will start to wipe again before cutting out if the rack is not at the end (ie in the middle). if its at the opposite end, the wiper will rotate the wrong way.

i would recommend taking it apart again and refitting and try and visulise how it should spin to ensure its the right way. also you could put 12v direct to it to test before refitting.

That was the answer I was looking for when I posted the thread. Would have saved me a lot of head scratching last night. :)

I tried running the motor in the case with no gears attached as part of my tests and it blew the fuse every time. I'm guessing it draws too much current without any load.

Anyway, I'm off out to put the theory to the test. :)
 

SilverSaloon

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how does the "park" feature work? as far as i could see, it just runs 12v to the motor for x amount of seconds. if the cogs and rack are aligned correctly it will just stop in the original position again.

am i missing something? although my R107 wiper mechanism is completely different to the one on my W124 i still also cannot see how the park feature works, from an electronic point of view...
 

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There has to be a micro switch on the cam that cuts the voltage to the motor at the park position, this is why if you do not hold the switch long enough, they will not park
 

Myros

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the park feature is just like the on on the main wiper

it's actually a set of points which keep the feed live to the wiper when it's away from the park position, even if you have switched them off. When the wiper comes back to the park position, the points open ( i think) and then the current dies and the wiper parks. When you next turn them on, the current goes in " normally", moves the wiper out of park, and the point system can take over if you have switched off.

They don't park properly for all the reasons given by the others, or that the wiper was only switched on long enough to not get the points open (or closed, i can never remember). So they don't park as the points haven't opened up yet. It's just like an old fashioned distributor set up, but with just one cam lobe.

Oh b*m. While I was writing this, malcolm summed it all up in one sentence.
 

television

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Re the mod,,I posted this some 3 years ago,,It must have gone when when my last computer crashed.

From memory, the mod to make them park was to add a cap or diode over the relay solenoid, so that it held on long enough for the wipers to park in the correct place
 
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roadhog

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Oh well, that mod sounds like something I'll have to do without. :(

However, after much faffing yesterday, success is all mine. :) For once theory worked in practice and I now have two beautifully working headlamp wipers. The little things in life....... :D
 


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