Beehive in AC Unit
Beehive in Attic
Beehive in Vent
Beehive in wall

Bees send scouts out to find a suitable nesting void. The scout does not care whether it is inside an AC unit, HVAC system, bird house, your attic, or your wall void. As long as there is an entrance and space the bees will come. Knowing this is the first defense against bees. Block up those holes or remove the temptation from the bees. Of course if you are too late you can take a glance at some of the common and uncommon places we find bees and their hives.
Here are some common and uncommon places to find bees and their hives.