Strange clicking sound from the vents

[linux2k]

I hear a faint rapid clicking sound coming from the vents, or least it sounds close - somewhere in the dash. I only noticed this recently. It happens when the car is cold i.e. it has not been on for 8+ hrs. When I push down on the accelerator to go from 0-40 mph the clicking is obvious. The clicking only happens during acceleration. But after driving for 10 mins or so it goes away. For example, after driving for 10 mins, there is no clicking when doing 0-40 at a traffic light.

I have had this car for just over three months and only noticed this clicking after the temperature dropped for the Fall season. Coincidence? Its a 2008 Altima S (CVT transmission).

Thanks

[sstroudwku]

It's the actuator motors on the HVAC system, just determining which one. We have a TSB for the A60/TA60 Titan/Armada/QX56 for the same noise. It sounds like a "thunk thunk thunk thunk thunk thunk thunk thunk" then you dont hear it again until it all resets.