‘Desert Rose’ had a failure of the driver’s door power window.
The mechanism seized up and needed to be replaced.

Window regulators on W116s are prone to failure due to binding of the gear mechanism.
The thin metal of the regulator bracket can get warped over time.
The electric power window motor does not have an automatic shutoff protection circuit.
Continuing to press the window switch after the window has stopped will eventually bend the bracket,
causing the gears to be misaligned, binding of the mechanism, and subsequent failure of the power window.

New W116 front window regulators are pricey.
I found a used PNP window regulator from a 1973 450 SE.
Luckily it was a newish replacement as evidenced by the non-factory access holes present on the door.

Being a 1978 W116 with the original window regulator, ‘Desert Rose’ needed to have three access holes drilled in the door sheet metal.
This is needed to allow removal of the electric motor, prior to removing the window regulator as per the instructions in the FSM for job 72-185.

http://handbook.w116.org/Chassis/72-185.pdf

My 1979 W116 ‘Stormcloud’ has the updated sheet metal with the three access holes pre-made by the factory.
A corrugated cardboard template was made to accurately drill the access holes on ‘Desert Rose’.

My 19mm Milwaukee Hole Dozer hole saw was used to drill the holes in the sheet metal.
Take care drilling the lower holes as the saw blade may buck due to the curved contours.
The saw blade may also buck when transitioning into the second layer of welded sheet metal at the frontmost lower hole.

The 5mm Allen head bolts were removed from the newly created access holes,
and then the damaged window regulator was removed after disconnecting the electric motor from the bracket.

DeoxIT Marine Mechanical grease was used on metal to metal points of contact on the window regulator
(gear teeth, gear shafts, regulator arm pivot), and Sil-Glyde was used where plastic parts would contact metal.
Sil-Glyde was also used to lubricate the rubber window channel, the sliding jaw bracket on the vertical guide rail,
and the window pane channel for the plastic glides of the regulator arm.

Reassembly was the reverse of disassembly.
Now I have a functional driver’s door window.
Yeah, no more need to open the driver’s door to enter the access code for the parking garage.

Attached Thumbnails

         

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022