Ticking noise from vents when turning on ac or heat

[4u33er]

I get a very low ticking noise when I turn the air on whether it be ac or heat. It's a continuous ticking and is driving nuts. It's not loud but enough to bother me when driving with windows up and no music.

What could it be?

[HUMTECH]

Best guess would be recirc door actuator without actually hearing it. Changed a few for same problem

[4u33er]

Where is the actuator door located?