Since last summer, whenever I turn on AC (auto mode), I could hear another set of sound on top of engine running noise. This new sound/noise goes up and down in pitch/amplitude when car acceleration. It was not there in previous 11 years. Also, cold air does not come out of vent as fast as before. It will take about 1 minute or more to feel the cold air.

AC system of my 530i has never been serviced since day 1 (12 years). What could be the cause of the extra noise when AC is ON ?

Thanks,

Ching-Ho Cheng

 

It's hard to say without hearing the noise. It sounds like it is belt-related due to the change in pitch with acceleration.

The cause of the delay in feeling the cold may be unrelated to the noise - and related to the 'freon' level in the AC system. You could be low.

 

I hope that it is belt related. Changing the belt is much cheaper and easier than compressor replacement.

 

I had similar problem, When the AC was on, I would get a noise, It would go away a little when moving..Turned out to be engine mounts.

 

Unfortunately, mine does not go away. It is not a squeaking noise, rather it sounds like engine noise and deeper in pitch. It only goes away when I turn off AC.

 

When the AC is on, the compressor clutch engages and there is a bearing behind that clutch that could squeak as it gets old.

My suggestion is to start the car, raise the hood, have someone turn the AC on and off and observe the compressor clutch and the timing with the noise. As you face the car, it is located on the lower left. You can find it by following the smaller belt.

Then take the belt off. Have someone turn the AC on and off with the car running again and see if the noise still happens. Spin the tension pulley by hand and see if you can reproduce the noise.

 

Thank you, I will try that this weekend.

 

I had a noise also when my air conditioner was switched on

It ended up being the serpentine belt

I put a new v serpentine belt and all the noise disappeared

 

Which belt did you replace, AC belt or serpentine belt ? E60 has 2 belts.

Thanks.

 

I replaced both belts but after I replaced the serpentine belt I put the old aircon belt on and the noise had gone

Then I replaced the aircon belt as well

My friend has a 2007 525i and she had a similar noise
I changed the serpentine belt on hers as it runs the aircon as well

Since replacing there has been no return of the noise
But I replaced with the v serpentine belt which is unbelievably quiet