See attachment, I have one rear door without this cover, however I've bought a donor car but I cannot remove this cover...
Any tips?

 

The missing cover is quite likely floating around in your door-panel. I've got one that comes off occasionally and makes metal-sliding noises on accel/decel maneuvers of sufficient magnitude. I refastened with a bit of RTV sealant as adhesive.

 

I am thinking this off the top of my head but if you pull the square piece of trim below the ashtray then undue the screw that holds on the trim on to the ashtray, you can then pull the ashtray off and hence the chrome. .

 

Correct on both accounts:

1) The chrome cover is just glued on, and over 20ish years tends to finally fall off. It probably slipped inside the door panel, or may be under your seat. Regardless of finding your original or one from a donor, you can just glue it back on. It has little locating pins so there is no risk of misalignment. A really easy fix.

2) To remove the switch and ashtray assembly, just pry off the vinyl cover at the base (inside the door "pocket") and behind that is a screw. Loosen the screw, then the whole assembly lifts out.

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