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I have a diesel Laguna 08. It has been giving a little bit of extra noise from the engine lately. I have noticed the one of the pulleys on the belt does not start like the others when the belt starts turning. This is the lowest one down in the engine and from looking at pictures it seems to be the AC pump.

This extra bit of noise I mentioned also has a delay to it and the noise seems to start at the same time that this pulley starts to turn — so my theory is that maybe there's a worn out bearing or something on the AC pump ( or it might be the power steering pump I suppose)

... but amidst all this I'm puzzled about why it has a delay to it - which means the belt is running over the pulley so the pulley is not turning for the first second or two after engine start.

This is my question - is this normal and if so why, and if not would it be a major issue. I was thinking that I'm not too worried if the AC pump bearings are starting to go I will just wait until it fails to replace it but now I'm not so sure.

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  • What happens if you repeat the test with the AC turned off?
    – Zaid
    Commented Mar 7, 2018 at 16:21
  • I will try that - didn't know there was a clutch on that so I hadn't bothered - thanks
    – byronyasgur
    Commented Mar 7, 2018 at 19:58
  • problem seems to be intermittent but I think it might be a bit of wear on the compressor clutch or something
    – byronyasgur
    Commented Mar 8, 2018 at 16:08

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The A/C compressor has a clutch mechanism that allows the compressor to be turned on and off. It is therefore normal to see the belt turning without the compressor running.

When the A/C computer wants the compressor to run, it sends an electrical signal to the compressor which operates the clutch. You should be able to hear a click as the clutch is operated.

If you watch this video @ 1 minute in, for example, you will see the disengaged clutch stationary while the pulley is turning.

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  • sorry I was just thinking about this - I'm actually confused now because surely if there was a clutch it would mean the pulley would be turning but the compressor wouldn't - whereas in my case the pulley is not turning but the belt is slipping on the pulley for a second or two
    – byronyasgur
    Commented Mar 7, 2018 at 20:01
  • @byronyasgur Are you sure the pulley is not turning? It can look like the pulley is not turning due to the clutch being mounted on the front of the pulley.
    – HandyHowie
    Commented Mar 7, 2018 at 21:38
  • @byronyasgur I have added a link to a video in my answer.
    – HandyHowie
    Commented Mar 7, 2018 at 21:44
  • thanks - that makes sense now - I brought it to my local garage guy and he didn't think it was much to worry about since the timing belt and water pump were recently replaced - but sadly ( lol ) the problem went away when i went in the garage - I'd say the clutch on the compressor might be just a bit worn or something and making a bit of noise - I'm not worried anyway as long as it's not something that could endanger the engine - thanks for your assistance
    – byronyasgur
    Commented Mar 8, 2018 at 16:07

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