A/C Compressor Not Engaging?

[baasacJak]

Beautiful weather at the weekend, right? First excuse to pop the ac on, chill the cabin out. Just got warm air. First thought, needs re-gassing since it's 5yrs old and has never had any recharge. Started to think about it, can't hear the extra tone that the ac compressor adds to the engine note any more. Cracked the bonnet open today, had someone toggling the ac and couldn't see or hear any change in the compressor. Anyone got any advice?

I understand that the belt always runs, on the compressor, but I would have expected to see the inner part of the wheel engage and start spinning with the belt. Followed by the extra, higher pitch tone of the compressor itself.
If there was an electrical fault (fuse or dead compressor) I would have expected an EMS warning?

Any advice or experience sharing would be appreciated.

[BenS]

Fuse might not trigger a fault, and it's easy enough to check before exploring other options.

[DavidDS3]

Loss of refrigerant possibly?

[baasacJak]

Fuse looks ok to me (untrained eye), and the diagnostic port worked the other day. Manual says it's on the same fuse. I'll try the diag port again in the morning, as there's a chance my fleabay reader has cooked it.

David, would the compressor "know" there's a loss of refrigerant with some sensor and not run (genuine question)?

[DavidDS3]

I believe there is some sort of pressure sensor in the system which if not activated say thru lack of refrigerant will prevent the compressor kicking in. The refrigerant also contains oil which lubricates the seals in the compressor. The idea is that if there is loss of refrigerant the compressor will not be damaged (expensive) through the seals being buggered.I have known situations where the refrigerant level is reduced but temperatures under the bonnet raise the pressure in the system activating the pressure sensor switch thus allowing the compressor to work. The only real solution is to take the car to an air-con specialist. if a leak is suspected they can put a dye into the system and hopefully that can locate the problem. Good luck

[Smithy225]

I had the same issue with mine a few months back. The compressor had failed and was replaced under warranty

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[lfcrule1972]

I was always told to keep the ac on all year round, as you can use it to heat in the winter and cool in the summer it's supposed to keep the parts working better as they're all lubricated throughout the year.

Doesn't help you I realise but touch wood it was only my first car with ac that had issues and it was a lot older when I bought it.

[baasacJak]

If anyone has time, could someone with working ac confirm the behaviour of the compressor when the ac is turned on, please?

All I want to know, really, is whether I should be seeing the side of the cylinder that the belt is on the outside of start to spin, pictured below. I know the belt always runs, so just the metal triangle (which I assume is the clutch) on the side, does that spin up when ac is on.



That will confirm to me that the compressor is not firing up. I'll get an ac man out to take a look, and can save him some time if I know that already.

Cheers

[baasacJak]

Just in case it is useful for anyone else, DavidDS3 was right about the compressor not coming on due to lack of pressure. Mine had 6g left in the system (out of the 500g +-25g that is specified in the owner's manual).

Had the ac fully serviced for £60. That included re-gas, uv ink, lubrication and a full once-over for leaks once the uv was in. Happy to recommend the chap that did it, if anyone needs.

To answer my own question, that triangular bit on the end is the clutch and it does spin when the ac is on & is stationary when the ac is off

Hopefully that helps anyone with similar problem in future

[eddiemunster]

To answer my own question, that triangular bit on the end is the clutch and it does spin when the ac is on & is stationary when the ac is off

You're right, it's the compressor clutch, often they fail as they pickup detritus from the road/engine and seize over time. It's always nice when it's a cheap (relatively so) fix! :-)