word9smith

I have searched and don't think this has been answered. I have a 1996 E320 and the issue is when I lock the car with the key the two back locks don't go down. The front locks do work. The actuators in the back doors have been replaced. I notice when I drive after parking and push the dash button the door locks on the rear doors do lock. How do I troubleshoot the vacuum power unit? Does anyone have pictures and vacuum diagrams? Thanks!