Focus Air-Con Stopped Working

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Sun 20 Mar 2005 12:37
Focus Air-Con Stopped Working - timp
My 1999T Focus's air-conditioning has stopped working. Just before the winter it was still capable of freezing my fingers off, but it now seems to have no cooling effect at all.

Throughout the winter I have switched on the air-con once a week for about 10 minutes (as seems to be recommended).

When I switch it on I here the 'clunk' of the air-con pump engaging, the revs drop slightly and the engine note changes, so it seems to be working mechanically. I also feel quite a bit of vibration through the car when it's on - whether that is because the idle speed has dropped or the there is a problem with the pump, I don't know.

Anyone any idea what could be wrong, or more importantly, how much it is likely to cost to fix?

This year it is due for a major service, a new battery, probably a new rear silencer (it's looking somewhat rusty), so I'm wondering whether to bother and just trade it in for a new one.
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Sun 20 Mar 2005 13:11
Focus Air-Con Stopped Working - Adam {P}
Hi timp,

I wonder if it needs regassing. Dynamic Dave posted a link a while ago about this and no doubt someone will be along with somethign more definite. I don't think a regass is too expensive; certainly not enough to make trading in the car an option. I think it's around 50-80 quid if of course that's what's wrong.

I've got a 1999T Focus and I switched it on for the first time since September yesterday. Very cold but it didn't smell too clever!
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Adam
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Sun 20 Mar 2005 22:00
Focus Air-Con Stopped Working - v8man
If it is very low on gas the compressor will not kick in as the pressure switch will prevent this.
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\"Nothing less than 8 cylinders will do\"
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Sun 20 Mar 2005 22:46
Focus Air-Con Stopped Working - Adam {P}
I don't know why I even look in the technical section let along post! That's twice I've been wrong today - both on a car that I own!
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Adam
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Mon 21 Mar 2005 20:15
Focus Air-Con Stopped Working - timp
I think boh v8man and Adski may be right. A perusal of the Haynes manual circuit diagrams suggests that the air-con will not switch on at all if the pressure is too low (or too high). Maybe the pressure is too low for a noticeable cooling effect but not too low for the system to fail altogether.

I'll book it in for a check in a couple of weeks and let you know what the outcome is. Thanks for your replies.
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Mon 21 Mar 2005 21:15
Focus Air-Con Stopped Working - elekie&a/c doctor
Focus a/c systems have a refrigerant gas charge of approx 750 gms.A 50% loss of gas over 5-6 years is quite normal & is enough to make the compressor engage but not enough to make the system work efficiently.
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Mon 21 Mar 2005 21:20
Focus Air-Con Stopped Working - Dave N
Timp is correct, the low pressure cutout is about 1.5bar. Normal static pressure should be about 5bar. The system will always read the same static pressure as long as there is liquid refrigerant in the system, no matter how little. Only when this last bit of liquid has gone will the pressure drop enough to shut down the system. I don't know the exact qty of gas, lets say 600 gramms, and the static pressure (dependant and always related to external temperature)is 5bar. If you reduce the qty of gas to 50 gramms, the static pressure will still be 5 bar. Think of it like an aerosol, you have the same pressure in a new tin as you do half way through. Only when the last bit of liquid has gone does the pressure tail off rapidly. This is one reason not to rely on the pressure switch to tell you when it's empty, as by then it really is

What concerns me a little is the revs dropping and the vibration. Sounds like a lot of extra load going on there. Have a go at turning the compressor hub by hand, see if there is a lot of resistance or if it feels rough. Do it with the engine off though!
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