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DerekW
Hi all,

Wouldn't you know it, the warm weather arrives and my a/c stops working.

When I switch it on there is a pause followed by a pronounced clunk - presumably the compressor clutch engaging - and the tick over revs rise slightly, I assume this means the compressor is working.

The sight glass on the top of the receiver/dryer shows continual movement of liquid within, this seems to indicate that there's ample refrigerant.

But out of the vents, even with temperature set to minimum, all I get is ambient air (24C). Moving the temp up to max produces a blast of hot air so this indicates that the temp selector panel is working.

There has to be a logical explanation but I can't see it. Any ideas?

Derek


DerekW
Further to that, the receiver/dryer has an electrical plug connected to the top, anybody know what it does?

Derek
robertmnorton
Hi Derek, it is the gas press sensor. If the quantity of refrigerant falls for some reason, normally leakage, ( suspect condenser straight away)then the vapour press also falls, this then signals the a/c control module to inhibit operation of the compressor,noticeable by the clutch not pulling in, you can see the clutch operation clearly.If clutch operation is ok when lower temp is demanded, then the probable cause is a blocked/failed expansion valve. This is mounted behind the bulkhead where the press and suction pipes enter. i believe it is removeable as the pipe fittings are an "o" ring sealed screw coupling.A full service may remedy the fault as an evacuation of the refrigerant is followed by a vacuum leak test,then by addition of the correct quantity of lubricant in conjunction with the correct weight of refrigerant.
aengus-xmv6
Hi Derek

are you sure the air mixing flap motor is working properly and not sticking part-way on it's travels, and so keeping a warmer mix?

You may be able to feel if it's moving fully end-to-end by reaching up under the glovebox area (remove lower trim panel first) and then adjust temp to max then min a couple times - there's a lever above the spindle. You could try helping it along when setting to min by pressing with a finger and see if that improves things.

If fluid is flowing past the sight glass then the compressor is engaged, and the refrigerant pressure is enough to allow the system to operate, but if the pressure is at the low end, then cooling won't be that great.

There's a couple of temp sensors too, one near the mixer flap motor, can't recall where the other is now, but I think these would stop the AC allowing the compressor to start if failed. Check the resistance, should be a couple K ohms ish, if open circuit or short, then will need replacement - at around £50+ from Cit.

regards
Dave
citroenxm
I agree with aeungus_xm,

EVEN with air con on, you can still select warm air and get warm air from vents..

So I would also bet its the Servo Motor on the heater controller has stopped working! Sticking the heating on 25 deg or so....

I think the heat one is the one by the drivers pedals, and not so bad, but still awkward to get at to change...

Rgds


C
aengus-xmv6
left hand side of the centre console, passenger side on RHD cars smile.gif
robertmnorton
Hi aengus, the other sensor is in the evaporator, it's purpose to sense over cooling ,which results in ice formation on the evaporator.Had this once on my old SED pulling up the Slochd.,got freezing fog in the cabin on a fine summer evening.
aengus-xmv6
ah that's the one, yes I've had that too, not very helpfully at night on unlit motorway - suddenly couldn't see a thing, and at damn near "no more license" speeds too!
DerekW
Thank you gentlemen, your advice gives me some things to check.

Derek
DerekW
Everything checked out OK, so today I called in our local a/c specialist. He found that there was just 55 grammes of refrigerant in the system instead of the 700 to 750 that should be there. He also said that normal loss rate was 15% per year so that wasn't bad for an eight year old car.

Car coolth has been restored, just as the weather turns cool.

Derek
Jan-hendrik
Congrats, Derek.
The sight glass on the receiver drier is no longer there on the very latest XM. This explains why:

The receiver-drier is used on the high side of systems that use a thermal expansion valve. This type of metering valve requires liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver is used. The primary function of the receiver-drier is to separate gas and liquid. The secondary purpose is to remove moisture and filter out dirt. The receiver-drier usually has a sight glass in the top. This sight glass is often used to charge the system. Under normal operating conditions, vapor bubbles should not be visible in the sight glass. The use of the sight glass to charge the system is not recommended in R-134a systems as cloudiness and oil that has separated from the refrigerant can be mistaken for bubbles. This type of mistake can lead to a dangerous overcharged condition. There are variations of receiver-driers and several different desiccant materials are in use. Some of the moisture removing desiccants found within are not compatible with R-134a. The desiccant type is usually identified on a sticker that is affixed to the receiver-drier. Newer receiver-driers use desiccant type XH-7 and are compatible with both R-12 and R-134a refrigerants.
wirdy
If there is anyone out there who wants a brand new R12 (Freeze-12) recharge kit just PM me.

I bought the kit to do my Pug 605, but sold the car before I used it.

The box contains tins of refrigerant and oil and the charging valves, etc. Has sat in my garage for 2 years, so they're anyone's for £25 plus postage.

They cost me three times that sad.gif but doubt I'll ever buy another R12-filled car and would like to see the stuff put to good use by someone here.

Much cheaper than converting to R134a. smile.gif
citroenxm
I'll have that for my 24v!!!


PM sent Wirdy


Rgds


c
DerekW
In like Flynn.

Derek
citroenxm
biggrin.gif biggrin.gif tongue.gif
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