Recently i began to get a strange noise coming from underneath/behind the dash/steering wheel. It's not speed related, it's not steering related. It seems to be related to the heat/ac. It's hard to describe the noise, but it sound like a creak. It's a quick creak like you would get if you moved in your leather seats. It seemes to occure on a timed basis about every 15 seconds or so but I haven't timed it. I happens weather the engine is on or not, as long as the key is turned to the on position. When the engine is turned off, it will continue for about 2 or three times, much like the shutdown of the heat/ac system. That's what makes me think it's related to this system.
The car is a 1991 ,525i, M-50 non vanos, auto, 194,000 miles, with individual temp. controls for the passenger and driver.

My daughter thinks it's a little man in there who's only job is to irritate me while I'm driving. Any thoughts on how to get rid of him?