I have a 2002 325i that just developed a chirping sound that is random and seems to be coming out of the driver-side air vent. It sounds like a canary warbling. Originally I thought it was caused by the air conditioning system, but it also continues with the air system off. Could it be connected with an air flow fan that is always on even if the system is off? Any suggestions? Thanks.
There's a very small fan which runs constantly to circulate air over the cabin temperature sensor. You can see it through the small grill next to the controls. Perhaps something is touching it - or the bearings gone dry. Try putting a vacuum cleaner over the grill to shift any foreign bodies.
Put a hankie over the nozzle, just in case there really is a family of small birds in there.
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