Having just installed a keyless entry system and examined the circuitry, I must say locks could be a 3 credit college course (MB Locks 101). There is a switch associated with each keylock as well as door open switches at each entry point. Locking circuitry recognizes if the driver's side door is open or closed. Passenger side operation is different than driver's side. Further, presence of a factory alarm adds additional factors. Were I troubleshooting it , I would ascertain that the vacuum pump were operating. Then ascertain that the drivers door lock switch is operating. Then check that the driver's door open switch is working. Maybe I'm not adding to the knowledge pool but I do wish you good luck and warmer weather. Incidently, reading the artical on installing a keyless entry system may be of help since it deals with these problems.

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1993 MB190e 104k