R107 Mercedes 350 SL (1973) wiper problem

[Marmight]

My 350 SL is undergoing a long term restoration job and the wipers have decided to park themselves in the middle of the screen. They work perfectly apart from this

Any ideas how to get them back to the normal park position?

Many thanks

Marmight

 

[Dec]

It will be possible to readjust the blades to the correct park position by disconnecting the motor from the linkage, this will allow you to move the blades down to their correct park position on the windscreen, the motor is then reconnect to the linkage.
If I had a picture of the motor and linkage I could explain it better.

Dec

 

[Marmight]

Thanks Dec, I think I follow what you mean...

Take the wiper motor off and remove the linkage. Push the wiper blades down to the corrrect position in park and re-connect everything back up again...now why didn't I think of that...DOH!

Cheers

Martin

 

[Dec]

Correct Martin, that’s what I mean, you will have to remove one nut at the motor to free the arms.
There is another way of doing it too, I didn’t mention it because I wasn’t sure exactly how it came about that the wipers are parking in the wrong place.

Was the wiper linkage ever removed or disconnected from the motor at any time before the fault happened?
or
Were the wiper arms ever removed at any time before the fault happened?

The other way is to remove the nut, under a cover, at the base of the blade and remove the blade from the spindle, then reposition the wiper arm to where it is supposed to be parked at the bottom of the screen then replace and retighten the nut, same applies to the other wiper arm.

Also, before you make any adjustments, be sure to switch ON and then switch OFF the wipers at the wiper switch and allow the motor a couple of seconds to finish its cycle and come to a stop before you remove the keys from the ignition.

Dec

 

[Marmight]

Thanks Dec,

I'm not sure if the wipers have been messed around with or not. Belinda (as she is affectionately known) went away for a top end overhaul after burning out a valve and came back many months later - a long story and a "so called" mechanic who thought he knew what he was doing but obviously didn't. Anyway, the wipers were working as normal when she went away and now they park right in the middle of the screen.

I switch on the wipers and they do a complete cycle parking in the middle!

Thinking about it, If I apply method 2, ie remove the blades and reposition them, when the wiper is switched on the wipers will try to enter the engine compartment surely? They will certainly strip the knurled ends.

I think that removing the linkage is the safer option.

I'll let you know how I get on when I get the chance to do the job - busy now till Friday and then off on hols for a week.

Cheers

Martin

 

[Dec]

Regarding method 2, as long as the wiper motor is parked, i.e. allowed to finish its cycle before you start making any adjustments, then the next time that the wiper motor is switched on, the blades will travel upwards so everything should be ok. You can check that anyway before you reattach the arms by running the wiper motor armless and watch the direction of rotation of the spindles.

However, I agree with you, method 1 may be the best approach.

It is more than likely that the mechanic did remove the wiper arms for safe keeping during the engine repairs and reattached them incorrectly by not insuring that the motor was parked before he started. I would presume that there was no reason for him to have removes or interfered with the wiper mechanism/linkage.

Let us know how it goes.

Dec

 

[Marmight]

Just got in from work and read your reply. Taken, as I am sitting in the car the wiper blades are practically upright. Switching on the wipers they travel to the N/S (where they should park), right over to the O/S and back to the middle where they now park so I suspect that taking the arms off and repositioning them will do serious damage to the spindles.

Method 1 seems preferable.

Many thanks Dec

Cheers

Martin

 

[television]

If the wiper arms do a full sweep in both direction but park in the middle of the screen,,this shows that the gears have jumped some teeth, and the gearbox will have to be re set up

 

[Dec]

Just got in from work and read your reply. Taken, as I am sitting in the car the wiper blades are practically upright. Switching on the wipers they travel to the N/S (where they should park), right over to the O/S and back to the middle where they now park so I suspect that taking the arms off and repositioning them will do serious damage to the spindles.

Method 1 seems preferable.

Many thanks Dec

Cheers

Martin

I accept your explanation, it dose seem that the original method is the right way to go, while the motor is parked ok what I am missing here is that it is parked in the wrong place (middle of screen) good job you didn’t follow my method 2.

Malcolm, I would say that it is the motor spindle that has jumped rather than the motor gearbox as the wipers seem to be working ok apart from the parking

Dec

 

[television]

I accept your explanation, it dose seem that the original method is the right way to go, while the motor is parked ok what I am missing here is that it is parked in the wrong place (middle of screen) good job you didn’t follow my method 2.

Malcolm, I would say that it is the motor spindle that has jumped rather than the motor gearbox as the wipers seem to be working ok apart from the parking

Dec

Yes I think that you are correct Dec on that.

 

[Marmight]

Thanks so much guys for all the input over this. I'm off on holiday from tomorrow and will get back to you with a full report sometime during the week after next.

It's really appreciated.

Cheers

Martin

 

[television]

Do have a good time,and we will still be here on your return

 

[Marmight]

Back from my hols and a spare day to mess around with the Merc. Trust Mercedes not to make anything simple, open the bonnet to find the wiper motor squeezed up into the corner behind the battery and with no room to see, never mind do anything! So...

Go under the passenger side of the dashboard and remove the two screws that hold the footwell panel in place. I suppose I should count myself as being fortunate and I don't have to completely remove the whole dashboard.

Remove the panel and up in the left hand corner, above the ECU is the wiper motor and mechanism. At the end of the motor there is a length of steel about 2" by 1/2 ", bolted at one end to the motor (main bolt) and at the other a pivoted fastening that connects with the wiper mechanism through an adjustable and elongated hole. The mechanism slides over the length of steel and is held in place by a captive bolt. This provides the rotary motion for the wipers. There is no need to remove the captive bolt.

Undo the main bolt (13mm) from the wiper motor and gently prise off the mechanism and steel arm from the wiper.

Move the wiper blades to the "park position" on the windscreen and, getting back into the cab re-connect the steel arm to the wiper motor.


Pull the wiper arms away from the the windscreen just in case...

Switch on ignition and the wipers and hey presto...the wipers work properly and rest at the right park position.

Replace the under dash panel and replace the wiper arms back on the windescreen - Job Done.

Many thanks to Dec and television and all for the suggestions and I hope my description is easy to follow.

Cheers

Martin

 

[Dec]

Thanks for the feed back Martin and glad you got it sorted, good job you didn’t use method 2, that could have made a right balls of the job.
Understand your description all right, it was just the main bolt that slipped on the motor spindle, there is a good illustration of the basic principle of a wiper mechanism and motor in action here… http://auto.howstuffworks.com/wiper1.htm

Dec