What year is the car? Vauxhall did modify the driver's door lock as the older ones caused problems. I changed a few when I worked in a Vauxhall dealership.

When I had a Cavalier Mk 3 I had the opposite problem - unlocking with the key would keep all other doors locked.

There are two switches on the back of the the driver door lock - one for lock and the other for deadlock IIRC. I would suspect one of those for a start. You will need to remove the door card and inner seal to get at it.

I spent hours on it and moine turned out to be the rubber cover on the switch had become less flexible and was most noticeable in cold weather.

I still have the Haynes manual if more information is needed. You could try simulating the lock switch on the door connector (by the hinge side). Let me know if you want me to loo up the pin numbers. This avoids removing the door card to investigate

Edited by Deryck on 27/08/2018 at 19:01