See if you can figure this one out!
 

at idle i hear a noise that sounds like a cross between a bad bearing and a fan blowing air. this only occurs if the temperature knob on the A/C is on the cold side, less than 21. If i rotate over to hotter temps, more than 24 degrees the noise "slows down" as it slows down it sounds like the noise you get if you blow up a balloon and stretch the opening so that it "screams". Just like with a baloon, the noise pitter patters out into silence. This is very wierd.

As i turn the knob back to colder temps. i hear a relay switch on, seemingly normal. this is probably just the thermostat for the A/C realizing that i want colder air and switching some valve open or closed. Also, as just as the relay clicks the noise starts up again sounds the same only in reverse.

is this some vacuum hose operated valve that has sprung a leak?

thanks, Mike

'87
944 NA
(114K miles)

I used to have an Alfa Romeo 75 (Milano) that did that. I figured out that it was the blower fan's bearing going bad. I theorize that as it gets colder, what is left of the lubrication in the bearing hardens to a point where it doesn't lubricate any more. Hence the squeal when it gets cold. It may be a stretch but you might want to check it out.
By the way, the Alfa is the WORST car I ever owned. It makes the Yugo look like a well built car. Complete lack of quality and engineering.

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Dave
1984 944
Stuck in hell with a year to go.

I can relate to the Alfa comment...When I was 16 I had the opportunity to drive a 164 quad somthing or other...believe it had 225 horsepower. Anyway it was just about brand new with approximately 6,000 miles on it. My grandfather allowed me to drive it in order to deliver it to the dealer for maintenance. Before I even got the car out of the owners driveway, the oil light came on! I thought I broke something...After two quarts of 10-40 the car was back on the road..briefly. 10 minutes later I dropped it off to its familar resting place - the Alfa dealer! Nice running motor - but the car was a nightmare!