Diagnose this squeaky noise from the engine bay, and only when the A/C is on
 

This is my 1984 944, driven back to Texas from Ohio just a week ago. During the 1,200-mile trip, the squeaking gradually got worse. What's wrong?

Please watch and listen to my video: https://www.youtube.com/watch?v=0EIREIRVgII

I appreciate any helpful advice. Thanks!

If it does go away then you need to check for bearing issues with the alternator, air conditioner compressor clutch or the power steering pump. Does the sound change when you turn the A/C on? If so that would be a clue. Do this first.

I'm also wondering what the serpentine and power steering belt tension is like. Sometimes if that or the power steering belt is loose or glazed it'll cause squealing problems. I'd look into this second.

If you've not isolated the issue by now, It could be just about anything. Water pump, alternator bearing, idler or sprockets bearings. The only way to find out for sure is to start with removing serpentine belt and power steering belt in succession to see if the sound goes away. If it doesn't then you know it's something inside the timing/balance belt area. At that point, I'd suggest you check your maintenance records to see when the water pump and belt rollers were last replaced. As a rule, the water pump is replaced every other belt replacement. The belts should be changed every 4 to 5 years and/or 30 to 40 thousand miles.

Just from the thread title I would guess a loose or glazed A/C belt. Check tension

If it only does it with AC on - then its because of the increasing load of the compressor.

Now, either the belt is old and needs replacing, or the compressor clutch or bearings, or internals are having issues. The first thing I would do - is replace that belt.

I had an opposite problem, I had a noise that went away whenever the AC was on. The pulley for the belt had sheared, and the AC clutch would grab it, and hold it in place, but when the compressor wasn't needed, it would squeal like crazy.

Thanks for all valued recommendations, I will look into them all and hopefully report back w/a favorable outcome.
I did notice yesterday that by building up enough rpm's prior to shifting into to first-gear, the squealing noises never materialized, even if it had been chirping a little at idle.

easy squealing solution
 

after months of squealing and belt replacement,belt dressing ........ i finally pulled the compressor. bearings seemed fine. cleaned the case, pulled the flywheel (?) free tool rental from obrians auto parts. what i found was tons of black stuff inbetween the two friction plates. really cleaned everything being careful not to damage the magnets on the flywheel. reassembled and remounted the compressor. the squeel is gone.:eek:

Wow, nice.

Shaft seal is done, no sense in charging the system until you replace it.

Congrats. Let's hope it's really gone - in my experience it just gets scared by all the commotion and moves to another component under the hood. :D

Someone listened to it recently and told me the chirping noise came from a bearing; and I do believe the noise is so sharp, metallic-sounding, and high-pitched it could not have come from a belt.
How many bearings are associated w/the a/c being turned on? Is it just the one inside the compressor; or could it be another in the pulley system?
I hope to get a listening device to better isolate once-and-for-all where the chirping is coming from.

The pulley bearing turns all the time if the compressor is off or on. Would have to be something inside the compressor or possibly a slipping clutch?