[george w]

The noise you're hearing is most likely a chirping or high pitched squealing sound. You may find that simply lubricating the motor may solve the noise. This is a very simple DC motor and the shaft bearings are exposed at both ends. Once you remove the aspirator from the dash structure it's very easy to access the motor. A light weight oil should do the trick. I lubricated mine using a pinpoint oiler purchased from a hobby store.

I noticed that you have removed the a/c compressor and lines. Since the ATC system blends cool and warm air I wonder how well it will regulate the heat output without the a/c system operating.

 

[ImperialCrown]

These aspirators can get very dirty with dust, hair, etc. (like a PC fan). Getting to it to clean it and a drop of oil on the motor bushings would be the first thing I would try.
Later cars went to IR (infra-red) sensors for interior temperature reading and the sensor 'eye' needed cleaning periodically also if the ATC operation got erratic.

 

[Oklahoma Wolf]

I would just clean it - these tend to cause problems when oiled. Last time I tried that on the Imperial, it started blowing fuses and I had to replace it.

Make sure you dust off the sensor, too - it's just a regular thermistor. It won't be far away from the aspirator.

 

[RaiRai]

Thanks for your tips. Now if I'll clean it properly, what do you say will I hear the motor running from driver's seat, when ignition on?

 

[RaiRai]

...
I noticed that you have removed the a/c compressor and lines. Since the ATC system blends cool and warm air I wonder how well it will regulate the heat output without the a/c system operating.

It has been regulating just fine. And I belive if A/C is not selected the system understands it can not use cooled air. A/C would still be needed in some cases, like traveling on highway on a hot day when there's someone on backseat, preferring top on.

 

[Oklahoma Wolf]

If it's working properly, you should have a hard time hearing it while it's working. I have to put my ear on the dash to hear it on the Imperial, though it's hidden back behind the cluster on that car.

Mine's been chirping lately... need do some cleaning myself. The Imperial's original worked only when it felt like it and the yard replacement did the same thing. That's when I tried the oil and found out what happens when that fuse blows while driving (system goes to full speed blower, full heat, and defrost). Let me tell you it's less than fun tooling down the highway in the middle of summer with the defrost vents blasting hot air at you.

And yeah... the system doesn't really care if the AC works on any of my cars that had it from the two '88 New Yorkers to the Imperial. It just runs the blower to full speed, full cold, on the dash vents. I don't think it even knows if the AC works or not... sure didn't on the Imperial when the ambient temp cutoff sensor failed.

 

[RaiRai]

I cleaned that funny looking sucker unit with vacuum cleaner and some paper. Then took a bottle of sewing machine oil and lubed the motor shaft ends with few drops. Test run with a battery charger, installed back and it is basically silent. Good.
I think will replace the motor if it gives me any issues from now on.