1992 mercedes 300e central lock system does not work

Hello, If the central locking system vacuum pump is not running through the normal circuit, check the relay for the pump. I'm not sure of the location, and I advise that you should secure a copy of the service manual to help locate it and to track through the vacuum system for the power locks. When the vacuum pump is running, if the locks are not functioning, you may have a leak between the pump and door locks, or the switch might not be actuating the vacuum lock actuators. This really is a strange system compared to nearly every other vehicle that uses electric door locks, and I strongly advise using the service manual to identify testing locations and procedures. You can find the cause, but be ready to remove some trim panels.