OK... This has been going on for too long now (year+).

Typically the A/C is on (Arizona after all) and we sometimes get a rapid-fire clack/clack/clack sound, I think coming from something up in the passenger side foot well. The clack/clack/clack noise... probably 3-5 clacks per second, goes on from 2 to 10 seconds, happens once every blue moon (like once a week... or so). Pretty sure this only happens when the AC is on.

No-one at Mini (Tempe) has a clue.

My guess is that there is an electronic servo actuated "blend door", mixes hot air with cold, being controlled by unstable electronics. But... that is a TOTAL guess... (based on a problem I once had with a Ford truck).

Cheers,
Doug

 

sounds like there's something loose in the fan/blower compartment. Take out the cabin air filter and have a look.

 

I think your guess is correct. It's one the servos that open the vent doors. Been there with a different car. I had to place a finger on them one at a time to figure out which one it was.