Noise behind dashboard

[kevin v]

My 1990 964 cabrio has just developed an interesting noise from somewhere behind the speedo /tachometer area ( and driving me to distraction!)
It sounds like the chirp of a cricket - a high pitched chatter. It's not an errent insect looking for a comfortable home - the sound is a not constant , it comes and goes and is not a body vibration as I can hear it when the car is stationary and engine running.
It also doesn't seem to vary with engine revs.
Any clues as to where/what I should investigate?

[Vandit]

It's either one or both of the blowers in the HVAC unit or possibly the fan that's on the back of the CCU. The motors start wearing out, creating the noise you hear, and eventually fail. Some have had moderate success by removing the blowers, reoiling the bushings, and reinstalling.

http://www.ccu.tore.bergvill.com/

http://privat.bluezone.no/toreb2000/ccurepair.html

[Resident Sicko]

Interesting. I have the same problem but has caused me to simply turn up the stereo or crack the window to hear the exhaust. : )

[Jim Richards]

I have this problem on the driver's side blower. It's not noisy all of the time, and usually quiets when I change the fan speed. Oh well, one of there days I'll do surgery on the HVAC unit.