Sounds like the driver's door switch is the culprit. There is a switch that goes to that door handle that is used to arm/disarm the alarm when the key is turned or when the car is unlocked with the master key.

First, check the vacuum lines to that door lock actuator. Make sure it's getting vacuum signal. Check by the vacuum pump and see if you have any cracked Y connectors there. Those like to rot out.

If you're getting good vacuum signal to the door, then put a hand vacuum pump on the actuator element. Pump it down and see if the door locks. Using the dial, see if the element HOLDS the vacuum. If it doesn't then it's got a cracked diaphragm and needs to be replaced.

That's a good place to start.


-tp