dead battery killed the electrics that power the lock mechanism?

Glad you got it open!

 

My 88S had central locking and I was able to lock it without battery, no problem. The mechanism does not rely on power, it is mechanical lock, electric actuator is only pushing an pulling the lock, but does not restrict it..

what MY is your car?

 

I also have a 1988 951S.

When the key is turned, and there is no resistance (such as unlocking a manual-lock door) or sound (actuators) when trying both doors & hatch.

I tried depressing the handle while turning the key as well as trying my spares; nothing worked.

After I changed the battery, the locks worked as per usual.

 

Regardless, I'm pretty sure the door should be able to be mechanically opened.

99% of cars produced today retain a mechanical lock on the driver's door - mainly so that the driver door can be locked or unlocked without electrical power.

I would see what the owner's manual says about it. And see if other MY '88 951S owners experience the same situation. User lovemypcar's works so I would imagine they all should.

There could be some sort of problem with the mechanical part of your lock. Such that, when you unlock it with the power connected, it actually relies on the central locking system to unlock it (or perhaps 're-unlock' - the driver's door when it is really unlocking it for the first time not sure if that's how the central locking system works). But that seems unlikely given that both doors and the hatch didn't work?

I'm not too familiar with the central locking system. But if it were me, I would want it to allow at least one door to be opened without power.

Take care,

 

Ignition key worn to the point that it won't work the locks anymore?