Just yesterday, I purchased a 1999 audi a4 knowing that it had a cracked centre diff. Upon inspection at home, I realized that I couldn't lock the car with the driver side key lock or the lock button on the panel. The remote doesn't have any batteries and I've pulled apart the door panel. I can see that when I turn the key, the locking system doesn't catch on the actual lock, it just kinda turns in place. However the passenger side will lock and arm the car but wont lock the other doors.

I decided that I will buy a new lock module for the driver side. So I put the door panel back together and started working on other things. later i tried to enter the car and as i opened the driver side door, all the windows rolled down. This wasn't happening before i took the panel apart.

Just wondering if there's anything else I can do other than buy a new part?

 

The doors lock & unlock when you lock/unlock the trunk.

Try that.