Have a 1999 Windstar van. When I unlock the doors with the control on the drivers side door, there is a loud buzz that comes from the sliding door behind the driver (also happens when you drive off & the doors automatically lock. Should I replace the door lock actuator?

 

Before replacing anything , would be a good idea to determine exactly what is happening that is causing the buzzing sound. There could be several possible reasons like ,lack of lubrication, faulty connections, something stuck in the assembly or the assembly itself is faulty.