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My Prestige has been low on A/C gas for some years really, should have had it topped up in 2001 when I had money, didn't, started to get less than cool when required in 2002 when money was starting to get tight. Had new consenser + overhaul by dealers when I got it in '98 (very expensive, but worth it). Since 2002 have been basically not been running the a/c except occasionally.

Started her up tonite, been trying to get the sounds working, main reason I've been driving the blue one is lack of sounds, oh and maybe the drive shaft is going or something.

Anyway, it was 23C outside, doing some ups and downs, tried AC, lights still fade and revs kick up a bit when turned on, and I'm SURE its still cooling a bit. Revs diminish when turned off. Am I overly optimistic in thinking it just needs converting off the R12 gas to new stuff and some new gas? Why did original condensor fail in 5 years but replacement one still seems to hold some gas after almost 10 more (admittedly it was on 113k miles in 1998)?

Did someone (Archman) here in Bristol area mention they used a mobile a/c man? Any recommendations appreciated.

There is a a/c place near work also, but I suspect they will just laugh at my XM sigh.

The VSX is OK but I just LOVE that old car, and the VSX fans are SOO noisy when its hot. The Preseige does ups and down much better tan the VSX too right now, can't wait to get hydraflush in there and see if it helps the power steering, which is somewhat stiffer than it used to be.
Funny you should mention this Tim, I need to get mine sorted too.

Does your compresser kick in even if there is little / no gas, or should it refuse to start in that situation? I'm not sure what the intended behaviour is, but it sounds like yours may just need the gas topping up...

Hi Ciaran,

Thats what I'm hoping. However I seem to remember previous discussion her that the S1 cars need converting to a new gas type also.

In the past I did notice that a/c seems to cut out after a few minutes (revs drop off, but light stays on) but tonight I didn't notice that.

Should I persevere and try and find someone who will fill it up with the original gas to save conversion?

Any input appreciated, especially if you have a S1 XM with A/c.

Ho hum, at least the VSX interior is more heat reflective than absorbtive, somethat you can't say about the all black in the Prestige, which really does need A/C when the weahther is like this.
I was going to try and offer some comparison with my car, but I don't know if that's going to help you much, as I don't think my compressor is starting at all. The rad fans startup when the switch is pushed and thats it.

I'm not sure if the not kicking in is electrical, or if its due to lack of gas. In your case, does it cool at all, or is it totally warm now? I wonder is there some kind of cut off which will stop the compressor if theres no gas? Would support the hypothesis that your gas is just low, but there's still some present.

How do you actually check the 'level' of it, if there is such a thing?


Although not XM AC I did have my C5s AC serviced last Saturday.

Here's what he did -

Connected a manifold block to the low and high pressure side of the system. The manifold had 2 gauges (low pressure and high pressure), 3 pipes (2 connected to the AC system and 1 to fill or evacuate the AC system), also a set of isolating valves. When he connected up the manifold there was a low pressure reading of 10 PSI, this wasn't enough to allow the AC to start up (a pressure stat is fitted so that if no gas is present it won't start the system to protect it). This was vacuumed out. Then a vacuum was put on the system and sealed, it didn't drop after 10 minutes so the system was considered leak proof. Then the vacuum pump was restarted and the valves opened, this was kept going for 35 minutes to remove any impurities from the system. Then using a precision scale 700g of R134a was admitted into the system with the AC running on maximum. The temperature of the air from the central vent was measured at between 3.2 and 3.4 degress C. What I did notice was that the high pressure gauge measurement altered as the fans ran and stopped. When the pressure got to 250 PSI the fans cut in then the pressure dropped within seconds to 200 PSI and the fans stopped.

The compressor on the C5 is a variable type and so is probably different to that fitted to XMs.

The guy who did it called the DIY bottles suicide bottles because you have no idea how much gas is in the system or if there are any blockages in it.

It only cost £30.

Hope the info helps.

When the system is low on gas the low pressure cut-out stops the compressor. My daughter, who drives a 1991 Volvo, had the system filled with R12 the other day. The dealer still has this gas. If your system has no leaks, DrTim, I would try to get it filled with the original R12, too. A retrofit/conversion to R134 will be costly.
I myself had the receiver/drier renewed a few weeks ago. This item should be replaced on a regular basis as the silica gel pellets get saturated, burst and clog up the system. I've had this with a BX 19GTi. Cost a bundle to fix that !

Read here about automotive AC:
Sadly the use of R12 (Freon) is illegal in the UK. The chap who came to look at my aircon says that he has had good success using R134a in an R12 system by using extra oil in the refrigerant. R134a is inferior in performance but better for the environment (Or not as bad).

QUOTE (bigjohnh @ May 9 2008, 11:26 AM)
Sadly the use of R12 (Freon) is illegal in the UK. The chap who came to look at my aircon says that he has had good success using R134a in an R12 system by using extra oil in the refrigerant. R134a is inferior in performance but better for the environment (Or not as bad).


The law functions in mysterious ways, doesn't it?
It seems that here the production of R12 is outlawed, but existing stock can be used in older systems that were designed for R12. Eventually vehicles that employ it will disappear. I am not convinced the UK (EU?) legislation really benefit the environment.
Naturally using R134a in a system designed for R12 is not a guarantee for optimal functioning of the A/C. Using extra oil isn't the cure either. Seals have to be replaced, as well as the oil and the receiver/drier. Good luck.

you could look around for someone who will top you up with R413 (I think) which is a drop-in replacement for R12 and will perform better in your system than R134. If you can find someone who still has R12 stock then they could top your system up, but it's very unlikely this far after the stuff was banned.

Problem with using R134 in a system designed for R12 is it won't cool as well, and unless seals etc are changed, you may end up with creeping black death in the system and then will need the whole thing sorting.

That said, a small top up of 134 seems to work ok wink.gif - but you won't find any cert'd AC specialists who'd do that for you...

If you think there's still gas in the system and want to give it a quick run up to see if it still works, you can force the compressor to engage by shorting 2 of the wires on the connector to the collector/drier - think it's the 2 thick yellow ones, but don't hold me to that as it's been a long while, so test before you try... or feed 12v via a fuse to the clutch (10A should do it). At least then you'll know if the system still operates before you pour loadsa money into it.

I found this on another forum:

R12 refrigerant is banned in most countries ( Montreal Protocol agreement). R134a has been used in place of R12 since 1992. Although R134a still contributes to Global Warming it does not destroy the Ozone Layer, as R12 does. There are at least 2 "drop in" replacement refrigerants for R12 on the UK market. I re-charge pre-1992 vehicles on a regular basis with RS24 refrigerant.

R12 was and still is superior in every way to R134a. R134a is being phased out and new refrigerants (Co2 and hydrocarbons) are in the pipeline.
Actually there is more. Check here for yourself dry.gif
Hi All

One thing that might be worth mentioning about this thread is that Citroen made the change over to R134A in 1992 so conversion from R12 is only needed on the early Mk1's. To tell which system was originally fitted to an XM look at the two pipes going into the back of the compressor. If the pipe connections are the same as the connection through the bulkhead into the cabin (single small bolt on a plate clamping the two pipes) then R134A. If they are separate connections with large nuts then R12 but even so look for a sticker on the panel by the radiators as R134A conversions should be marked in this way.


Hi Xmexec,

Citroen DID NOT put R134a into the XM untill Series 2 in 1994....

As you know, my 1993 XM SEi V6 was on R12, untill I converted it with Series 2 System...

The unit in the dash DOES NOT need changing, however, everything else under the bonnet does, R134a pipes are also thicker in diamiter...

I had the R12 air con in the S1 24v re gassed last year by a Self employed Air Con expert, he also used an R24 gas of some sort, he vacd the system down, but discovered a VERY minute leak.. HOWEVER, even thought she has sat in my field for 8 months, the system HAS HELD the pressure, as the compressor still cuts in and nice cold air comes out the vents, and that was on Sundays 25 deg temp!! I agree R12/24 is MUCH MUCH colder then R134a


This has turned into a very interesting thread, thanks for the copious amounts of information everyone has posted.

I must actually investigate my (January '90) S1 and see if its been converted to any other gas. There are some stickers from an aircon servicing company on the slam panel, but they're too faded to read. Still, I'll see if I can recover anything, it would be interesting to see what gas has been used if its had any recent work.

My guess is that it will still be on R12,

As xmexec says above theres a couple of clues to the R12 system

I dont think many people know that the system can be changed from ~R12 to R134a just by replacing all the nunder bonnet components...

Must buy another S2 V6, so I can convert the S1 24v to 134a...


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