A/C whining noise with revs

Allworth · 09-30-2023, 01:32 PM

Hi all,
There is a whining noise coming from A/C system that fluctuates with engine revs, when above 2,000 it seems to disappear. As soon as I press A/C button off - noise dissapears, even if fan is working. Had an AUC sensor error, replaced the sensor - error gone but the noise still there, so unrelated.

I am suspecting that A/C is giving extra load on V-belt thus wearing tension pulley could be the culprit.

Any thoughts?

(I should add that I have 118k miles on the odometer)

Portly · 10-01-2023, 01:57 PM

My A/C has been making the whiny-belt noise since I purchased the car with 30k miles (50,000 km) on it. I now have 120k miles (190,000 km) and, to my astonishment, the A/C is still working fine. I kinda think that's "just how it is" with this car, though perhaps others have different experiences.

gregthegr8 · 10-01-2023, 10:42 PM

I'll chime in too as I've been researching this of late and seem to hear/read 3-4 various things people say are the cause/fix.

It's only in recent weeks, at about 44k miles, that my a/c has started to make a slight additional whine/whir/not sure what to call it. Increases with RPM, and goes away if I turn the a/c fan or a/c button off (fan still blows). Haven't looked under the hood with it on/off yet to check it out. Seems like several people have had various things replaced to deal with this only to still have it there and many reports of dealerships just saying it's "normal" and "how it is."

It's slightly annoying, but not sure how big of a deal it is or if left alone/not addressed, if it'll develop into something worse. My biggest fear is some shop saying it needs a new condenser or pulley or belt, I pay through the teeth, and the noise is still there. I've seen other reported fixes of recharging the system, adding a/c oil to the condenser or something, etc.

Any input or an a/c support group would be greatly appreciated.

maxwmiller · 10-11-2023, 12:19 PM

Allworth,
Turning "on" and "off" the A/C button engages and disengages the compressor. "On" puts additional load on the engine to run the A/C cooling system, which increases RPM at idle. It is normal for A/C "on" to cause a constant, noticeable but not overwhelmingly loud noise, especially under 2000 RPM.

Assuming your serpentine belts are in good shape and you have an appropriate amount of refrigerant in your system, there's not a cause for concern. It is almost a guarantee for an A/C system to get noisier as it ages.

Gregthegr8,
In general, the A/C system really doesn't need much maintenance. Belts are cheap and easy to DIY, replace them every 4 yrs/50k miles. If the A/C won't blow cold, look into getting a recharge. Otherwise unless something fails, there is no need to throw money at a slightly noisy but otherwise perfectly functional system.

Also I cannot stress this enough, do not DIY an A/C recharge! Yes, auto parts stores sell recharge kits. They usually forget to mention that these come with a significant risk of "overcharging" the system, which will destroy it in seconds and cost $1000s to repair. Just go to a local shop.

gregthegr8 · 10-12-2023, 01:58 PM

Quote:

Originally Posted by maxwmiller

Gregthegr8,
In general, the A/C system really doesn't need much maintenance. Belts are cheap and easy to DIY, replace them every 4 yrs/50k miles. If the A/C won't blow cold, look into getting a recharge. Otherwise unless something fails, there is no need to throw money at a slightly noisy but otherwise perfectly functional system.

Also I cannot stress this enough, do not DIY an A/C recharge! Yes, auto parts stores sell recharge kits. They usually forget to mention that these come with a significant risk of "overcharging" the system, which will destroy it in seconds and cost $1000s to repair. Just go to a local shop.

Thanks for the advice. I haven't investigated it too far yet, though it is getting a lil louder I think, but will check it out under the hood with a/c off and then on to see if i can locate where the noise may be coming from such as a belt or pulley. Belts definitely have NOT been replaced since I've had it (almost 5 years) and it blows cold. And yes, I'd rather not throw/waste money at a slightly noisy thing, lest it might lead to some ultimately further and costlier damage down the road due to my procrastination or laziness.

Allworth · 10-18-2023, 04:48 PM

Just to take pulleys out of the equation;
I had to do a maintenance, because of a squeaky noise on a cold start, so replaced idle pulley and tensioner with a pulley. Squeaks gone, a/c still whining.

backslashv · 07-06-2024, 05:08 PM

Allworth Did you ever figure out the cause of the issue? I am facing the same.

Allworth · 07-07-2024, 01:07 PM

Quote:

Originally Posted by backslashv

Allworth Did you ever figure out the cause of the issue? I am facing the same.

Short answer: no.
But I have some arguments to conclude its to do with a A/C compressor itself,
as I have changed idle pulley, tensioner pulley, belt, crankshaft pulley, replaced alternator pulley to one with a clutch. So this covers pretty much all auxiliaries beside alternator bearing and A/C unit itself, so gives me enough confidence to say its A/C unit. And it seems to be reasonable to let it be as long as its functioning properly.

maxwmiller · 07-11-2024, 02:52 PM

So my system wasn't blowing as cold as I wanted, which is very noticeable when it's been highs of 110F in CA for a week. Maybe two or three minutes to actually cool the cabin. For context, my serpentine belt snapped in early May, which may have messed with the AC system.

I bought a proper A/C manifold + gauge set and discovered my R134 levels were a little low, readings were 20PSI low side and 140PSI high side at 100F outside temp with engine at operating temp. Added .2 pounds and got system up to 30PSI low 230 PSI high. AC blew much colder, but more interestingly, the whining of my AC compressor became much less noticeable when the system is fully charged.

And yes I know the technically proper way to do it is to fully evacuate the system, run a vacuum, check for leaks, properly measure refrigerant blah blah but I don't want to let out refrigerant into the air and don't have the super fancy machine to capture it. I know it's a closed system and shouldn't leak but at some point everything leaks a little, it wouldn't be surprising if in the last twelve years it lost a little gas.

My theory is that the compressor is out of whack and makes noise when the refrigerant is low. Might be encountering too little resistance, not lubricated, etc. Will keep updated

gregthegr8 · 07-12-2024, 05:06 PM

Just for some follow up and completeness on my issues and journey to silence, I went the easy route first thinking it might be the blower motor as it is for many people. So, took that out, cleaned it out, and oiled/lubed that up and reinstalled which seems to solve the issue for some people. No change for me and I struggled mightily to get it out and back in (even though it should take 10-15 minutes for most people). Shapes.

Even ordered a new blower motor, twice, but they kept arriving with broken tabs, so gave up and took to an indy shop to investigate since it was then starting to not even blow that cold anymore. Turns out, I was just very low on refrigerant, which they said is VERY common at the 10+ year mark. They recharged the system and voila - ice cold, no more whining/moaning/wheezing noise.

So, it could be as simple as that, though many seem to have different causes and hard to tell how different the noises are that people are experiencing.

09-30-2023, 01:32 PM	#1
Allworth Lieutenant 267 Rep 523 Posts Drives: X1 xDrive20d (E84) Join Date: Jul 2021 Location: Stoke-on-Trent iTrader: (0)	A/C whining noise with revs Hi all, There is a whining noise coming from A/C system that fluctuates with engine revs, when above 2,000 it seems to disappear. As soon as I press A/C button off - noise dissapears, even if fan is working. Had an AUC sensor error, replaced the sensor - error gone but the noise still there, so unrelated. I am suspecting that A/C is giving extra load on V-belt thus wearing tension pulley could be the culprit. Any thoughts? (I should add that I have 118k miles on the odometer) Last edited by Allworth; 10-03-2023 at 10:35 AM..
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10-01-2023, 01:57 PM	#2
Portly Enlisted Member 13 Rep 40 Posts Drives: X1 XDrive28i, M2 Join Date: May 2015 Location: Iowa iTrader: (0)	My A/C has been making the whiny-belt noise since I purchased the car with 30k miles (50,000 km) on it. I now have 120k miles (190,000 km) and, to my astonishment, the A/C is still working fine. I kinda think that's "just how it is" with this car, though perhaps others have different experiences.
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10-01-2023, 10:42 PM	#3
gregthegr8 Admiral of the Fleet 275 Rep 3,560 Posts Drives: Cars Usually Join Date: Jan 2008 Location: Los Angeles, CA iTrader: (5)	I'll chime in too as I've been researching this of late and seem to hear/read 3-4 various things people say are the cause/fix. It's only in recent weeks, at about 44k miles, that my a/c has started to make a slight additional whine/whir/not sure what to call it. Increases with RPM, and goes away if I turn the a/c fan or a/c button off (fan still blows). Haven't looked under the hood with it on/off yet to check it out. Seems like several people have had various things replaced to deal with this only to still have it there and many reports of dealerships just saying it's "normal" and "how it is." It's slightly annoying, but not sure how big of a deal it is or if left alone/not addressed, if it'll develop into something worse. My biggest fear is some shop saying it needs a new condenser or pulley or belt, I pay through the teeth, and the noise is still there. I've seen other reported fixes of recharging the system, adding a/c oil to the condenser or something, etc. Any input or an a/c support group would be greatly appreciated.
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10-11-2023, 12:19 PM	#4
maxwmiller Private 11 Rep 86 Posts Drives: 2013 X1 xDrive2.8i Join Date: Dec 2022 Location: CA iTrader: (0)	Allworth, Turning "on" and "off" the A/C button engages and disengages the compressor. "On" puts additional load on the engine to run the A/C cooling system, which increases RPM at idle. It is normal for A/C "on" to cause a constant, noticeable but not overwhelmingly loud noise, especially under 2000 RPM. Assuming your serpentine belts are in good shape and you have an appropriate amount of refrigerant in your system, there's not a cause for concern. It is almost a guarantee for an A/C system to get noisier as it ages. Gregthegr8, In general, the A/C system really doesn't need much maintenance. Belts are cheap and easy to DIY, replace them every 4 yrs/50k miles. If the A/C won't blow cold, look into getting a recharge. Otherwise unless something fails, there is no need to throw money at a slightly noisy but otherwise perfectly functional system. Also I cannot stress this enough, do not DIY an A/C recharge! Yes, auto parts stores sell recharge kits. They usually forget to mention that these come with a significant risk of "overcharging" the system, which will destroy it in seconds and cost $1000s to repair. Just go to a local shop.
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10-18-2023, 04:48 PM	#6
Allworth Lieutenant 267 Rep 523 Posts Drives: X1 xDrive20d (E84) Join Date: Jul 2021 Location: Stoke-on-Trent iTrader: (0)	Just to take pulleys out of the equation; I had to do a maintenance, because of a squeaky noise on a cold start, so replaced idle pulley and tensioner with a pulley. Squeaks gone, a/c still whining. __________________ 1995 E34 525td auto • 2016 F30 320ed auto
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07-06-2024, 05:08 PM	#7
backslashv Second Lieutenant 113 Rep 251 Posts Drives: 2022 BMW M3 Competition Join Date: Apr 2015 Location: California iTrader: (0)	Allworth Did you ever figure out the cause of the issue? I am facing the same.
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07-11-2024, 02:52 PM	#9
maxwmiller Private 11 Rep 86 Posts Drives: 2013 X1 xDrive2.8i Join Date: Dec 2022 Location: CA iTrader: (0)	So my system wasn't blowing as cold as I wanted, which is very noticeable when it's been highs of 110F in CA for a week. Maybe two or three minutes to actually cool the cabin. For context, my serpentine belt snapped in early May, which may have messed with the AC system. I bought a proper A/C manifold + gauge set and discovered my R134 levels were a little low, readings were 20PSI low side and 140PSI high side at 100F outside temp with engine at operating temp. Added .2 pounds and got system up to 30PSI low 230 PSI high. AC blew much colder, but more interestingly, the whining of my AC compressor became much less noticeable when the system is fully charged. And yes I know the technically proper way to do it is to fully evacuate the system, run a vacuum, check for leaks, properly measure refrigerant blah blah but I don't want to let out refrigerant into the air and don't have the super fancy machine to capture it. I know it's a closed system and shouldn't leak but at some point everything leaks a little, it wouldn't be surprising if in the last twelve years it lost a little gas. My theory is that the compressor is out of whack and makes noise when the refrigerant is low. Might be encountering too little resistance, not lubricated, etc. Will keep updated
	Appreciate 0 Quote

07-12-2024, 05:06 PM	#10
gregthegr8 Admiral of the Fleet 275 Rep 3,560 Posts Drives: Cars Usually Join Date: Jan 2008 Location: Los Angeles, CA iTrader: (5)	Just for some follow up and completeness on my issues and journey to silence, I went the easy route first thinking it might be the blower motor as it is for many people. So, took that out, cleaned it out, and oiled/lubed that up and reinstalled which seems to solve the issue for some people. No change for me and I struggled mightily to get it out and back in (even though it should take 10-15 minutes for most people). Shapes. Even ordered a new blower motor, twice, but they kept arriving with broken tabs, so gave up and took to an indy shop to investigate since it was then starting to not even blow that cold anymore. Turns out, I was just very low on refrigerant, which they said is VERY common at the 10+ year mark. They recharged the system and voila - ice cold, no more whining/moaning/wheezing noise. So, it could be as simple as that, though many seem to have different causes and hard to tell how different the noises are that people are experiencing.
	Appreciate 0 Quote