Vehicle Lock Repair: what to note first

After a cold night the driver's door key barely goes in, and when it finally seats it stops halfway and will not turn any further. Meltwater from the day before ran into the keyway and the overnight drop in temperature sealed it solid.

Worth answering before the call

Is the vehicle reachable and stationary right now, wherever it is parked? Is there any sign of water or corrosion around the affected lock? Do all the other doors and the trunk lock and unlock normally?

My key turns but the door will not open. What does that usually mean?

A key that spins without effect points to the connection behind the cylinder rather than the cylinder itself: the linkage rod that carries the turning motion to the latch has likely slipped off its clip or broken. Reconnecting or replacing that rod typically restores normal operation.

What causes a car door lock to seize up in winter?

Meltwater from a thaw can run into the keyway during the day and refreeze overnight, and road salt and brine thickens grease inside an older cylinder. Both make the key resist turning or stop partway, and both respond well to gentle warming or a lock de-icer rather than force.