AC humming buzzing whining noise

[conn]

So as spring has passed and AC is doing more work now (we had like 27 C outside for a while) I have noticed humming / buzzing / whining noise of the AC at lower RPM. If it is really hot outside, then the noise is louder, since AC has to work harder.

 

It is really easy to test. Make sure AC has to do some work, stand still, turn off start/stop, be in neutral / park (as I got DSG) and then give it just a little bit of rpms to just over 1k. Reapet giving slight notches of gas peddal. I hear distinct noise (this can be heard even when driving and taking from the standstill). Turn off AC and the noise is gone.

 

For notes AC works good - I am set at 21 degrees, sometimes +/- 1 depending of passangers.

 

By the way one more question about AC consuming petrol at 16-17 degrees C outside. I have noticed AC consuming something like 0.1-0.3 L/h even if I turn my car heater up... This might be nothing, but still a bit annoying.

 

For notes I talked to the service person and he said, that some clients have returned to them with the same "problem". For one they even changed AC compressor, but it supposedly did not solve the noise problem.

 

For notes nr 2 in the cold weather I do not recall hearing that noise - I suppose AC was used just a little, but I can't remember hearing that...

 

 

There is one more thing you could check if your car does this or not: if you have a longer ride than 30 km could you check if your car does tsst-tsst-tsst noise on the left front side of the engine (tsst has 2 sec interval - some pressure is being released). Supposedly it is related to air conditioning... At least the service person told me that.

You can hear that tsst in this video I made:

https://www.youtube.com/watch?v=Dyhj0zkFeEs

Turn up volume to hear it - fades out relatively quickly.

 

I haven't been able to record that AC noise on my mobile - waiting for hotter weather at the moment.

[Rob123]

at very low temperatures - below 6 degrees, (maybe 4 ??) the AC is not used, even if the light is on. I'm fairly sure it say in the driver manual, but dont remeber for sure.

At temperatures above that, it will be used. Even if you set the internal temp to 28 degrees, and its 10 degrees outside, A/C will still be on, if the light is on.

There are occasions when the AC is on or off, when you ask it to be the opposite, not sure why, but generally only at a time when it shouldnt be noticable.

As for the noise, bare in mind, it is a compressor, like a fridge uses, and its on a clutch mechanism for turning on and off. this may well make a whining or buzzing noise. cant say i noticed it on mine, but i've not often been out of my car when its running, and probably wouldnt think too much of it if i had heard it.

And for the pressure releasing noises, the AC does work under pressure - well half of the system is pressurised, which is how it works - so it could be the pressure equalising once the system is turned off.

I'll have to wait until we have a nice day over here to see what my car does / sounds like

[Phil-E]

If it's quite a prominent noise there could be a fault.

 

In our old car we had a humming/whine noise that gradually got worse then one day smoke came from the bonnet in a traffic jam at 32c external temp in Germany and the compressor packed in!

 

Phil

[andyvee]

at very low temperatures - below 6 degrees, (maybe 4 ??) the AC is not used, even if the light is on. I'm fairly sure it say in the driver manual, but dont remeber for sure.

At temperatures above that, it will be used. Even if you set the internal temp to 28 degrees, and its 10 degrees outside, A/C will still be on, if the light is on.

There are occasions when the AC is on or off, when you ask it to be the opposite, not sure why, but generally only at a time when it shouldnt be noticable.

As for the noise, bare in mind, it is a compressor, like a fridge uses, and its on a clutch mechanism for turning on and off. this may well make a whining or buzzing noise. cant say i noticed it on mine, but i've not often been out of my car when its running, and probably wouldnt think too much of it if i had heard it.

And for the pressure releasing noises, the AC does work under pressure - well half of the system is pressurised, which is how it works - so it could be the pressure equalising once the system is turned off.

I'll have to wait until we have a nice day over here to see what my car does / sounds like

The A/C is a variable pressure system, not just on or off. So if your interior temp is set to 28 degrees the compressor will be doing zero work as the valve will be open and it won't be pressurising the system. It is not a clutch driven system like a fridge at all.

[Rob123]

ah, advances in technology...

I assume it'll still work with the humidity sensor, so if you have the temp set high, but its as humid as a sauna, the AC will kick in to dehumidify.

Plus, there'll still be a compressor to make the whinning or buzzing when it is working

[conn]

OK I understand. One more thing that noise is heard inside the car.. So I do not know - will have to see what it does in the long run. Got 5 years warranty, so it might be just my ears being a bit a**l for noises.

 

(PS, I never heard my 2006 Mazda 3 FL do it)

[andyvee]

If it is inside the car it isn't the compressor.

Sent from my HTC One X using Tapatalk

[bletch]

Think I got the same problem...

 

Today was the hottest day in Norway in ages with 33c. AC worked perfectly when driving home from work. However, at evening when temp had dropped to 22 I heard a similar buzzing/whining sound after acceleration and when pressing the gaspedal. Like a turbine. It disappeared when turning off AC.

 

It has never sounded like that in 5 months even in similar conditions last days. It does seem to work but the sound is very noticeable...

 

So it seems like a similar issue at OP has. Have you solved your problem?

 

And, if its not the compressor then wonder what the problem can be. Are going abroad with car tomorrow so cant call dealer until monday. Just hope AC wont fail as its supposed to be just as hot the next couple of days...

Edited 24 July, 2014 by bletch

[bletch]

Had problem writing on phone so got two posts... Sry.

Edited 24 July, 2014 by bletch

[Mohamad]

i have the hissing noise 3 times in 2 sec intervals as you described & it happens after i shut down the car & get out of it i always hear it , also 2 friends with the same car have the same sound, i think it is not related to A/C as i hear it even if the A/C was not used at all during the journey , but i think it is normal it may be related to the Turbo or something.

[conn]

I am going for 15 000 km oil change on 12.08 and will be asking what's up with that "whine". Still works perfectly at 30 degrees C - no problems.

 

It would be interesting to know how the hissing is related to the turbo - anyhow, it seems it is normal after all :-)

[Mohamad]

I am going for 15 000 km oil change on 12.08 and will be asking what's up with that "whine". Still works perfectly at 30 degrees C - no problems.

 

It would be interesting to know how the hissing is related to the turbo - anyhow, it seems it is normal after all :-)

 

i think the HISS is very normal as it is in my car since day 1 , the same to the 2 cars of my friends & it is very consistent every time you make a journey then park , i always hear it.

[bletch]

I forgot to mention my car is a 1.2 tsi. I took it to the dealer who looked and listened to it and will replace compressor on warranty. So mine was a faulty ac..

The tdi on the other hand is known for some turbo noise after shutting down the engine as described in a pinned thread...

[Andy P]

I've noticed mine makes a noise which I can only describe as hearing a neighbour strimming their garden. It of course stops when the ac is off.

[conn]

Anyhow, I talked to the rep. They took a brief look at the AC components and could not find anything wrong + there are no errors either. Soo for now I will settle with what I have got, but may be in the future I might take that cheese with "whine" - 4 and half years of guarantee left