How to Solve Rear Window Sun Shade Folding Motor Gear Replacement.
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1) Removing the seats is actually optional in W140 W124 E31 E32 E34 A6 A8 100 . The description of how to do this is in the other thread - Rear seat bottom pull up at the front, move forward, detach the reclining cables from either side of the seat, remove seat bottom from car,
2) Seat backs - remove outboard headrests, pry square cover off, 12 mm socket to disengage reclining shaft, (optional, but worth it - 10 mm bolts x 4 to detach seat back bottoms - remove from car)
3) Side covers above deck to rear glass - pull door gasket off pinchweld, peek at top front button which is not a nylon connector but slides forward to disengage, pop off panel toward center (three stubs) at the top (they may fall free or stay in sheet metal - find them and place in panel for later) there are tabs which connect this panel to the rear shelf, pull forward to disengage.
4) Rear shelf - unclip 4 buttons at front edge, disconnect 3rd Brake light - driver's side. Lift shelf up and forward, dropping along seat belt path, this may require reaching back between shade assembly and brake light to lift and disengage there.
5) Shade assembly - There are two 10 mm bolts holding the shade assembly to the shelf, you can see them through the glass - but not reach them. Disconnect wire harness - driver's side. Take shade assembly to the workbench.
2) Seat backs - remove outboard headrests, pry square cover off, 12 mm socket to disengage reclining shaft, (optional, but worth it - 10 mm bolts x 4 to detach seat back bottoms - remove from car)
3) Side covers above deck to rear glass - pull door gasket off pinchweld, peek at top front button which is not a nylon connector but slides forward to disengage, pop off panel toward center (three stubs) at the top (they may fall free or stay in sheet metal - find them and place in panel for later) there are tabs which connect this panel to the rear shelf, pull forward to disengage.
4) Rear shelf - unclip 4 buttons at front edge, disconnect 3rd Brake light - driver's side. Lift shelf up and forward, dropping along seat belt path, this may require reaching back between shade assembly and brake light to lift and disengage there.
5) Shade assembly - There are two 10 mm bolts holding the shade assembly to the shelf, you can see them through the glass - but not reach them. Disconnect wire harness - driver's side. Take shade assembly to the workbench.
Gear and motor basics: some of this is covered above, here is my version: (Do NOT open the gear housing until you read these notes)
The shade arms are controlled via tubular arms acting on a pivot at the outside bottom edge of the assembly. The tubular arms are attached to a yoke attached directly via keyed fit to the motor shaft. This shaft is part of the larger metal gear in the motor housing. Notes: The large metal gear does not spin per se but moves through about 120 degrees to deploy and retract the shade - most of the gear teeth do not see contact with the smaller gear in normal function (except at the factory - I will explain below). The metal gear and spring can be left intact in the gear housing but this is dumb because teeth bits are all over in the grease. There is a 'stop' which prevents the metal gear from unwinding but his requires that the metal gear stay deep in the housing. I am not sure how tight the spring is supposed to be - I got one additional revolution past the resting position using needle nose pliers in the gear holes (what is a 8 point socket!) and felt that was tight enough. That step is unnecessary if the factory technique below is used.
Motor/ gear function - The motor must sense when it is at the extremes of movement and stop and prepare for reverse movement. The motor spins a screw which engages the plastic teeth (which were chewed up) on the smaller gear which transfers rotation to the brass center gear which engages on the larger metal gear which is part of the spindle - moving it the 120 degrees (1/3 revolution) to move the tubular arms which control the pivoting shade arms.
The shade arms are controlled via tubular arms acting on a pivot at the outside bottom edge of the assembly. The tubular arms are attached to a yoke attached directly via keyed fit to the motor shaft. This shaft is part of the larger metal gear in the motor housing. Notes: The large metal gear does not spin per se but moves through about 120 degrees to deploy and retract the shade - most of the gear teeth do not see contact with the smaller gear in normal function (except at the factory - I will explain below). The metal gear and spring can be left intact in the gear housing but this is dumb because teeth bits are all over in the grease. There is a 'stop' which prevents the metal gear from unwinding but his requires that the metal gear stay deep in the housing. I am not sure how tight the spring is supposed to be - I got one additional revolution past the resting position using needle nose pliers in the gear holes (what is a 8 point socket!) and felt that was tight enough. That step is unnecessary if the factory technique below is used.
Motor/ gear function - The motor must sense when it is at the extremes of movement and stop and prepare for reverse movement. The motor spins a screw which engages the plastic teeth (which were chewed up) on the smaller gear which transfers rotation to the brass center gear which engages on the larger metal gear which is part of the spindle - moving it the 120 degrees (1/3 revolution) to move the tubular arms which control the pivoting shade arms.
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