Binding windshield wiper linkage, most likely caused by rust in the arm rod collar.
Remove the arms and bezel, spray the collars with WD40, and turn on the wipers (with car running).
Let the wipers run for 30 too 45 minutes, spray the collars and linkage with WD40 every 3 too 4 minutes.
If there is no physical damage = bent or broken linkage, you should be back to normal operating speed.
Reassemble and test with a garden hose.
Have a great day.

__________________
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

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