Remove the cowling from under the windshield, engine bay side. You want to remove the cabin filter. Turn on the AC, turn up the blower speed if needed, and spray a bunch of Lysol or autoparts store evaporator deoderizer specific spray, directly into the air intake where the filter used to be. Shut down the engine and give the spray a few minutes to kill the bacteria that causes the smell. Install new filter.

The cause of the odor is shutting down the AC and engine at the same time, leaving a bunch of water in the evaporator core. Newer Volvos will operate the blower after shutdown to help the evaporator dry out, extending the life of the evaporator.

I typically shut down my AC about 1/2 mile from home (if I remember) and it no longer drips water on the driveway or garage floor.

Klaus
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Always willing to listen, just not able to take direction.