I have a 1998 Audi A4. My central lock stopped working

If it is cold enough the mechanism could be frozen. If not the actuator is gone and will need to be replaced.

check main plug for door

the best solution for that problem is to be referred to read the manual

The black control box in the right side of back bumper that control the central locking is named "Vacuum Pump Electrical Module for central locking"

unlock car with key/hold over for 30 secs then lock car with key/hold over for 30 secs then unlock with remote hold button down for 30 secs.this should reset system.

The 1996 A4 uses a central locking system which is vacuum operated. Each door has a vacuum servo which raises and lowers by air pressure created by the vacuum pump. The pump is located in the trunk right behind the passenger side tail light.

Either the pump is faulty or the vacuum lines leading to it are damaged.

This problem may be best left to the Audi dealer to troubleshoot as this is very model specific and not many small shops will have experienced this problem.

it is more than likely the drivers door latch assembly

LEG CameraB (1989)
Bond 43 Opere

Try disconnecting the both leads to the battery, wait 30 seconds and reconnect. Hope that helps.

sounds like a blown fuse