110 Air Conditioning Air-conditioning
Citroen XM Internet Reference Version 1.0 167
3/3/99
110 Air Conditioning
Could anyone with experience of the air-conditioning system advise what a hissing noise inside the car
might be caused by. I’ve noticed the noise over the past few weeks whenever the compressor is running
(and the radio isn’t). I don’t think it has lost any refrigerant. Is it likely to be terminal?
The car is a 1991 V6 auto with 98k miles on the clock.
As far as I know the only thing that can be responsible for that sound is indeed the loss of refrigerant.
Under the bonnet near the radiator must be something like a ’bottle’ however not made out of glass
which has a little ’window’ on top. If you see little bubbles in there the system is empty and needs a refill.
You should be able to get a refill for about 50 GBP. (Maybe a bit more for the R134 system).
Burning out
I’m planning to get my Air Conditioning regassed (on my XM). However one of my friends recently
caused a 1000 pounds worth of damage to his car (a saab) by failing to get his air con oil refilled when
the air con was regassed.
What seems to have happened is that the air conditioning compressor has seized, burning out the
clutch completely. So, new compressor, more gas etc.
The first thing the repairers asked was did you get the oil level checked.
Does anyone know if the XM also works the same way and how to check the oil?
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It all depends on exactly which compressor you have, the ability to add oil, and the quantities are not the
same, but as a general rule, check the compressor for a large (5-8mm head size) screw on the upper
outside face, close to the rear. This is quite often labelled "Oil" on a small blue/silver sticker.
If it’s there, you can remove it and look inside for oil. If you’ve ever topped up the dashpot on a Mini or
similar, it’s the same kind of job. Use an oilcan and 15/40W engine oil, but it takes a very small amount,
don’t fill it to the brim (it expands when hot !). This really is the kind of job best left to the A/C man.
Your friend should claim against the firm who regassed his AC, it is supposed to be part of the regassing
job, checking the oil level.
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If the car was originally filled with R12 (a CFC) it will have used a mineral oil this will depend on the age
and the intended market. In the UK R12 is no longer generally available so is now generally replaced
with R134a (a HFC) this requires a change to a ester oil i.e. synthetic. Never open any plug or
disconnect any pipe on a refrigeration system the release of any refrigerant is illegal And in the UK can
lead to a prison term. When changing from a CFC to a modern refrigerant it is not a one time/shot job.
The old refrigerant will have to be recovered the oil changed and new refrigerant added but as the oils
do not mix this has to be repeated as many times as necessary to flush the old oil. The oil must be
tested every time.
With industrial plant it takes upwards of 3 times. And the cost start at £1000 per compressor but that
includes many times more refrigerant. A car will take 0.25 - 1 kg per charge an industrial plant 15 kg
upwards per charge at a wholesale cost of £12 per kg.
Three more things the new refrigerants have smaller molecules so any small leaks you have that have
little effect now will seem like very much largerleaks. Next a car compressor has a shaft out to the pulley
this will have a plastic/rubber shaft seal and we do not yet know the effect the new oil refrigerant
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