Help needed to try and diagnose air-con noise

[XCF]

Hi,

My 2010 XC90 D5 has a noise from the engine near the compressor / alternator when the air-con is turned on (and the car is running).

The air-con works but can anyone suggest ways to try and narrow down the source - e.g is it the compressor or maybe the air-con clutch ? or something else I haven't thought of.

Thanks

[gmonag]

The AC compressor is often noisy. I think you have diagnosed the issue.

[tonygreen1966]

I had a slight noise coming from my air con pump when the air con was switched off(pulley freewheeling). When air con was on there was no noise. It was just a very slight noise and I assumed it was just the air con clutch. Sometime later the ancillary belt broke (had to call out the RAC). Turned out the air con pump clutch was knackered and the pulley was not freewheeling smoothly and the belt was rubbing against it which heated the belt then the belt literally melted the plastic pulleys on the tensioner and PAS pump until the belt finally snapped. When the belt broke I was able to turn the air con pump and feel that the clutch was knackered as it was not spinning/freewheeling freely. If I was you I’d remove the air con pump belt(ancillary belt) and see if the pump pulley spins freely. You may as well check the alternator clutch pulley (yes it has a clutch too) at the same time - there are some guides on this forum.
I was lucky, as when the ancillary belt breaks it very often gets into the timing belt cover and breaks that belt and knackers your engine. The ancillary belt can break prematurely due to the aforementioned and also alternator pulley failures and belt tensioner failures so consider replacing these parts if you are having work done in this area.

[john langrick]

Hi, mine made a loud noise when operating. Note that when you start the car, that air on pump switches on at the time you operate the ignition whether air con is on or off.

I thought my starter was staying engaged until I changed the pump.

Now all quiet.

Mine is a much older car and really wanted to keep costs down, so I ordered a new 'nissens' pump, which my indie installed and runs perfect and quiet.

At the same time I changed serpentine belt as with all the noise generated there must have been excessive wear.

Hope this helps

[XCF]

Thanks so for. I’ll check to see if I can hear the noise at startup but once running the noise starts when the aircon is turned on, and stops when turned off.

[john langrick]

Hi, mine switched on and off, that is the functio n of the clutch I believe. Certainly on mine it was not constantly on, even in the hottest weather.

I can only assume the motor is temperature controlled as it would switch on for about 10 seconds, then off with a huge contrast in noise.

Now I cannot tell if it is running or not.

If yours is constantly noisy when ac on, I suspect there may be other issues perhaps being affected.

There is a connector on the side which provides power when ac operates and hence engages clutch. There is an earlier thread on this. You could disconnect and isolate the pump.

John l

[gmonag]

The pump cycles on and off when ac is running (as it usually is with climate control). Watch the pump with the engine running. You will see the clutch plate on the pulley close and the pump run every few seconds. If the noise is constant suspect the pulley. If it starts when the clutch engages, suspect the pump. Having said that, they can work ok for years whilst making a noise. It's personal preference if you choose to change it, as long as it works.

[XCF]

Thanks for the info. Yesterday in traffic the noise was cycling on / off every 30 seconds. It would be on for about 8 seconds, then off for 30 and repeated.

The noise for the 8 seconds is similar to the sound from a pneumatic drill, only very very much quieter (just about audible in the car with the radio off in stationary traffic).

Given the cycle on / off sounds like this is the pump ?or could it be the clutch engaging ? (8 seconds of pump time seems quite short ?)

[gmonag]

8 seconds sounds about right. So, it is your pump that is making the noise. I'd leave it alone for a while and monitor it. If the noise becomes excessive or the ac stops working properly, consider replacing the pump.

[XCF]

Thanks - much appreciated.