Whirling Sound While AC is Turned On, Matches Up With RPM

[JamesSam]

Recently while driving I had my AC on and it started to make a low volume whirrling sound that increases and decreases with the revs in acceleration and deceleration. Still blowing ice cold. When the hood is open it definitely sounds like it is timing belt related. Is this the sign of something bad to come? Is there any adjustments someone may know I can do to prevent anything that may happen next?

 

[JamesSam]

My first instincts tell me that this has something to do with the compressor in the timing belt. It seems to echo through the exhaust when the AC is on. When the AC is off it sounds normal. Any info will help. Currently I am looking through the service manual trying to pin point where to start troubleshooting. Anybody??

 

[Goldie Driver]

No timing belt on these engines- perhaps you meant timing chain but you would be hard pressed to hear a noise unless it was so loose it was slapping the timing cover. We had a similar situation with our 77 Suburban when it was newer ( 4 or 5 years old) and since it 100% matched engine revs I was thinking transmission. Nope - bad AC compressor.

 

[JamesSam]

No timing belt on these engines- perhaps you meant timing chain but you would be hard pressed to hear a noise unless it was so loose it was slapping the timing cover. We had a similar situation with our 77 Suburban when it was newer ( 4 or 5 years old) and since it 100% matched engine revs I was thinking transmission. Nope - bad AC compressor.

I just had an initial feeling it was in the timing chain, sorry not belt. I said that because I was thinking about the serpentine belt running around the compressor.

 

[JamesSam]

So is it possible an adjustment can be made or should I anticipate replacing the compressor?

 

[Goldie Driver]

So is it possible an adjustment can be made or should I anticipate replacing the compressor?

Take the belt off the compressor - it is separate from the others - and lets find out together !

If the noise goes away , there ya go. Of course, no AC w/o a belt, but ...


Well, I say that. Your 87 may have a serpentine belt. Then I would unplug the power plug at the compressor.

 

[squaredeal91]

Alternator whining?

 

[hey mister]

A/C off...no whine.
A/C on...whine.
Might be compressor or compressor bearings.

If A/C on = whine, compressor is on borrowed time.
Ohh, that rhymes....kewl..

 

[JamesSam]

Alternator whining?

Yes

 

[squaredeal91]

Yes

While idling remove and plug in alternator plug to see if it changes

 

[JamesSam]

While idling remove and plug in alternator plug to see if it changes

Ok...are you saying I need to remove the AC compressor while the engine is on and plug in the alternator plug to it????

 

[squaredeal91]

Ok...are you saying I need to remove the AC compressor while the engine is on and plug in the alternator plug to it????

No lol. Simply unplug alternator plug while idling to see if the sound goes away or comes back. Assuming the sound is now heard all the time. Or is it literally on an off sound with a/c on and off? Plug Should look like this.

 

[Ricko1966]

Ok...are you saying I need to remove the AC compressor while the engine is on and plug in the alternator plug to it????

Earlier post, he wrote alternator whining? You responded yes,so he's talking about checking the connection to the alternator. If the noise is only present with the A/C on . I suspect it's the compressor or if you're lucky the compressor clutch. I really think there's not much to do I suppose you could take the belt off and turn on the A/C to verify the noise is gone. The reason I said turn on the A/C is just to make sure the load from the A/C clutch isn't messing with the alternator.If the noise is gone,start shopping for an A/C compressor andcreciever drier,before you fill the system with trash from a self destructing compressor.

 

[JamesSam]

No lol. Simply unplug alternator plug while idling to see if the sound goes away or comes back. Assuming the sound is now heard all the time. Or is it literally on an off sound with a/c on and off? Plug Should look like this.

Literally only when AC is on is the sound present. When no AC everything sounds normal.

 

[squaredeal91]

Literally only when AC is on is the sound present. When no AC everything sounds normal.

Okay. Probably safe to say it's the compressor if the sound is consistently on and off with switch.