Air Con Noise - Clutch or Compressor?

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petef
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Air Con Noise - Clutch or Compressor?

Post by petef »

I have a problem with the air con on my Series 1 Xantia Activa. After starting the car and switching on the air con, after a few seconds there is an audible click and the clutch can be seen to engage on the side of the compressor. The air starts to blow cold and then the cooling fan kicks in – and at the same time there is a terrible screeching noise. At first I thought it was the fan bearing, but, on investigation, the noise was found to be coming from the compressor/clutch unit. It lasts a few seconds, then returns each time the fan cycles on and off until the car is warmed up when it disappears. The air con itself works fine – it was 35 degrees yesterday so I should know…
My question is - where is the noise coming from – the clutch or the compressor itself? The clutch can be replaced with the compressor in situ, whereas if the whole compressor has to be replaced, it will obviously be more expensive and the system will need re-gassing adding to the cost. I will probably start with replacing the clutch unless advised otherwise, but wondered why the screeching doesn’t start immediately the clutch kicks in. The noise sounds like a knackered bearing somewhere…….?
The auxiliary drive belt was recently replaced but the noise was present both before and after. I will attempt to provide the YouTube link so the noise can be heard. In fact, if you are within 100m of the car on start up, the noise can be heard…..

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white exec
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Re: Air Con Noise - Clutch or Compressor?

Post by white exec »

The complaining noise seems to coincide with the fans kicking in.
Speed of the aux belt seemed to fall as well.

That would also be when a lot of extra load is placed on the aux belt by the alternator having to work extra hard.
Try
1. pulling the fuse(s) for the fans, and then seeing what happens as the AC comp kicks in and out
2. seeing whether it's nothing to do with the AC, by leaving it switched off, and then calling for more alternator output by switching on HRW and all headlights, etc.

Aux belt noise (which it doesn't sound like) can be checked by squirting some water (NOT WD40) at the aux belt while it's making noise.

A 'listening stick' (length of wood, narrow pipe, or very long screwdriver) touched on the suspect object (eg alternator casing, or compressor body) might help pinpoint the source of the noise. It is fairly dramatic.

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petef
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Re: Air Con Noise - Clutch or Compressor?

Post by petef »

Thanks for reply.
Not sure if the air con will work without the fan being in the system. Certainly on my x7 when the fan failed last year the air con kicked out after about 5 seconds.

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EDC5
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Re: Air Con Noise - Clutch or Compressor?

Post by EDC5 »

I agree with the comment above, it does seem to coincide with the alternator load increasing (from the fans).

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petef
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Re: Air Con Noise - Clutch or Compressor?

Post by petef »

The noise is certainly generated when the fan kicks in, not when the air con clutch engages. Further investigation with a metal pipe 'listening stick', as advised, certainly points towards the noise coming from the alternator rather than the compressor. Also when the noise starts as the fan comes on the alternator output drops from 14.3v to about 13.8v before climbing back up and the noise disappearing. Didn't realise that a high load on an alternator could make it screech like that - presumably because a bearing is on the way out?

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white exec
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Re: Air Con Noise - Clutch or Compressor?

Post by white exec »

That does sound like an alternator bearing giving up.
Try it again, using lots of lights, heated window, and blower (on high speed) to see whether this sort of load does the same thing.
Under high load, the tension in the alternator drive belt will increase, and put a bigger load on its bearings.
If the alt is the culprit, probably best just to get an exchange one, unless you're good at stripping these things down.

Other possibility for the noise is if there is a tensioner/jockey wheel operating on that same belt. These have bearings too, and can wear out. The car might not have one, though.