We have a regular slow popping (clicking) noise when the ignition is turned on coming from within the right side of the dashboard. If you press the recirculate button on the air conditioner it stops. The air conditioner, heater, and fan all work fine.
It sounds like one of the vent doors is sticking. I hate to say it, but you need to craw under the dash and identify which one it is and see what is causing it to stick. It could be a faulty actuator or the vent door itself may be stuck.