My first suspicion would be the bushings need lubrication, and/or the filter is plugged.

You will need these links.

W124 Blower Motor Removal Photos
W124 Blower Motor Removal Photos - PeachParts Mercedes ShopForum

MONO BLADE VERTICAL parked windshield wiper
windshield wiper

Hesitating Wiper Repair
http://202tech.mkosonen.com/howto/wiper.html




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__________________
ASE Master Mechanic

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D

https://www.boldegoist.com/