I'd have to check my car to double check, but I'm 99% sure the trunk lock is vacuum activated. It must be, because mine still locks and unlocks with the doors even though the electrical actuator isn't working.

So, assuming the trunk lock still works, remove the rear seat pad and find the central locking vacuum pump. Get yourself an air source and pump air down the rubber hoses until you find the one that controls the trunk lock.

Any kind of pump will work if you can connect it to the hose, I have a syringe pump that comes with a pack of children's party balloons which works fine.

(Just had a thought. Check the position of the key slot in the lock first. If it's vertical, the above should work. If its horizontal, you're SOL)

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1987 300e manual 250,000 km (sold)