Windscreen Wiper Problem

[rsawatson]

Evening,

Have driven back from Cornwall today in appalling weather, albeit without any problems, except a small (but annoying!) one to do with the windscreen wipers.

The dilemma is that, when on, the right hand wiper overshoots the rubber on the windscreen and keeps knocking the wiper blade out of the runner. When adjusted on the splines, the wiper just ends up slapping the bottom of the windscreen.

Is there any way to reduce the length of the sweep that the wiper takes when it moves? I've had a look in the manuals, but the mechanism seems quite complicated for the novice and I wouldn't want to make a fatal mistake!

Expertise needed!

Thanks,

Ryan.

[charlie_morris_minor]

i changed the wiper wheel boxes last night and have the same problem.. but i have changed to a 2 speed motor and have clap hands.. looking forward to lots of fun on sunday trying to see what has happened, i will let you know the out come..

[rsawatson]

Yes please do, it's always reassuring to hear that you're not the only one with the problem...

[bmcecosse]

No - the sweep is decided by the gear wheel in the motor - the angle is usually stamped on the gear. Someone may have fitted an incorrect replacement motor. Of course - wear and tear sets in - allowing the arms to flail about rather more than they should. It is possible to remove the arms - carefully mark the spindles (tippex!) - then withdraw the rack - turn the spindles 180 degrees - then re-insert the rack (which can also be turned over if suspected of being worn) and check the spindles have ended up 180 degrees (approx) from where they sat before. Refit the arms - and you are now running on unworn rack and gear teeth - should be like new! The arms of course also develop some slop - so it may not be perfect - but surely worth a go!

[rsawatson]

Hmm it sounds as though you know what you're talking about, unfortunately, with this one, I don't! It's disheartening to hear that it can't be adjusted. I was just flicking through a previous forum on a similar topic, and by the looks of things they tried everything you just said and still had the same problem.

It wouldn't be so bad if the wiper blade actually stayed in, instead of flapping about everywhere!

Thanks anyway.

[bmcecosse]

Is it possible the arm is just loose on the spindle - or perhaps too long - or too long a blade fitted ? Only minutes to take the lid off the wiper motor gearbox and see what 'degree angle' is marked on the wheel. Youcan of course also move the arm round one spline on the spindle - it will now not sweep so far in one direction - but will sweep further in the other direction!

[mike.perry]

If the wiper blades are moving erratically it is often because the wheel boxes are not clamped tightly to the rack, allowing the outer casing to move about. Remove the glove boxes and watch the rack for movement and then tighten the clamp screws on the wheel boxes.
If this is not the problem then try removing the offending gear wheel, rotating it 180 deg. and replacing it so that the rack is working on an unworn section of the gear.

[bmcecosse]

Yes - that's worth checking - although removing gloveboxes is not my idea of 'fun'!

[rsawatson]

Thanks both for your ideas, will check out and get some techies at my local branch to take a look. Incidentally, I just popped out to try and adjust the offending arm on the splines, but couldn't release the arm off as I couldn't persuade the retaining clip - too tired and fed up with it to mess about now.

I'm still not clear on how the mechanism actually works anyway. What's the job of the 'rack' and the 'wheel boxes', etc? Does the gearbox driven by the motor in the engine bay drive a reciprocating cable which in turn acts to drive the motion of the wipers?

[bmcecosse]

Yes! Rack and pinion.

[charlie_morris_minor]

No - the sweep is decided by the gear wheel in the motor - the angle is usually stamped on the gear. Someone may have fitted an incorrect replacement motor. Of course - wear and tear sets in - allowing the arms to flail about rather more than they should. It is possible to remove the arms - carefully mark the spindles (tippex!) - then withdraw the rack - turn the spindles 180 degrees - then re-insert the rack (which can also be turned over if suspected of being worn) and check the spindles have ended up 180 degrees (approx) from where they sat before. Refit the arms - and you are now running on unworn rack and gear teeth - should be like new! The arms of course also develop some slop - so it may not be perfect - but surely worth a go!

normally i would agree with the statement.. and am sure i have in the past but.. my wipers worked fine, other than one side parking on the body as opposed to the window. All I have changed is the wheel boxes, if there was wear in the wheel box would that no give less rather than more movement?

Yes - that's worth checking - although removing gloveboxes is not my idea of 'fun'!

thats why it can wait until sunday.. and i will report back on sunday with the number of teeth on the wheel box gear wheels

[mike.perry]

Wear in the rack or gear wheel teeth would reduce the wiper arc on a dry screen but may well increase the arc on a wet screen as the wiper slips around.

[MarkyB]

And increase even more the faster you go due to the air pressure pushing too.

[charlie_morris_minor]

sorry guys did not get around to doing the wipers today.. had to DIY around the house before the in laws arrive

[Kevin]

Only minutes to take the lid off the wiper motor gearbox and see what 'degree angle' is marked on the wheel.

Dont forget to mark the cover position if you remove it as it can affect the parking position of the wipers, and needs to go back in exactly the same position.

[LaughingBoy]

The sweep/arc of the wipers does not only depend on the gear wheel in the motor gearbox. I have replaced my original clap hands single speed motor which had a 100 degree wheel with a 2 speed motor which also has a 100 degree wheel. The wipers now go way off the screen! It seems the wheel boxes also affect the degrees of sweep - the common 32-tooth wheelbox gives more sweep than the 40-tooth wheelbox.

[bmcecosse]

Still - 100 degrees is 100 degrees....so should have made no difference. Did you also change the wheelboxes at the same time?

[LaughingBoy]

No, all I have changed is the wiper motor.

Yes I agree bmc - you would have thought that 100 degrees is 100 degrees full stop, and I went to some trouble getting what I thought was the correct 100 deg wheel only to find the arc/sweep is too big.

It's strange and I'm wondering if it's possible that it's the combination of motor gearwheel and wheelboxes that give the correct arc. Thus for example my wiper motor came from a car with 40-tooth wheelboxes the combination of which gave a sweep of 100 degrees but fitting the same motor to a car with 32-tooth wheelbox gives a larger sweep. This would also explain why Charlie's wiper sweep increased when all he did was change the wheelboxes ... he never got back to tell us the result of his investigation.

[philthehill]

The sweep/ throw is also dependent upon the distance the wiper rack crank pin is from the gear centre point i.e. the further the crank pin is from the gear centre point the more throw there is and the result is a bigger sweep of the wipers.
They may be all the same distance but worth a check.

[charlie_morris_minor]

sorry for the delay..

my problem was that my wheel boxes were also lose, when i did them up though I was unable to open the bonnet as it hit the top of the arms! so i had to put some washers between the wheel boxes and the spacers ( inside the car ) to pull everything back in, allowing me to open the bonnet and the wiper arms no longer sweep off the edge of the glass.