Is there any way to open the trunk of a 91 benz 500sl when the master key or fobs doesnt work. it was damage in a attemped break in

Have you tried using the switch on the mater panel on the dash? Have you tried hitting the key-fob or using the master key and pushing down on trunk lid while turning? How was the lock damaged during the break-in? What did they do to the lock?

It sounds like a vacuum related problem. The pump works as your doors locks are working. I think you should check the vacuum lines to the trunk lock. Could be the line is cracked in a way that pressure seals the leak and vacuum opens it. Try replacing the line (or just run another line out in the open to test before replacing).

This one stood out for me as I have this intermittent problem as well; or, the locking/unlocking could isn't a problem, but the LED behavior is identical to yours but more often than not it works correctly. I wonder if it's a lack of power? You must have already tried the re-synchronization procedure? I've never taken apart the vacuum pump that un/locks the trunk, but you say it works? Can you disconnect the vacuum line to verify there is pressure/suction from the line itself? I wonder if these trunk lock latches are prone to grease/gunk build up where it makes it harder, over time, for the locking mechanism to engage and disengage?

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