Windcreen wiper motion W124

[MB250TD]

The wiper on my 1995 W124 does not always 'park' in the correct position - and this is especially annoying on intermittent. Indeed it parks in virtually any position, depending where in the cycle I turn it off. The wiper blade is new and my windscreen is clean and 'rain-away' treated. I have regreased the pistion and mechanism under the turtle shell, and used electrical contact cleaner on the relay. The windscreen wiper motor is vigorous. Might I have a problem with the control stalk in the car? Any ideas gratefully received.

 

[Tiff]

Does the intermittent wipe work OK?
If yes,I would suspect the park switch inside the wiper motor.

 

[MB250TD]

Yes, the intermittent works, but like medium and fast settings, parks anywhere! Is access to the park switch inside the wiper motor feasible, or is this problem indicative of need for a new motor? The motor is strong. If a switch / contacts are the problem, then I assume that these can be got at, but no doubt this is a labour intensive task which is either expensive or requires some know how! Has anyone done this and can advise? Many thanks for the help so far.
John