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Old 24-09-2004, 07:22 PM   #1
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Question R12 refrigerant conversion to what?

What is the current acceptable gas that is used as a replacement for systems running R12a? I mentioned R49 to one local firm and they said no to that one. They said they used R134a in conjuction with a special extra type of oil that sat on top of the standard oil. I was told that R18 and R49 gases would destroy the rubber seals if left in contact over-winter, and that they were no longer used.

Is this true? Is 120 to convert a reasonable price?
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Old 25-09-2004, 08:50 AM   #2
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I've just been studying refrigeration gases but I can't remember.

I'll check on monday morning
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Old 26-09-2004, 11:41 PM   #3
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I have been using R49 for 7 years now, no problems at all. You can also use RS24.
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Old 27-09-2004, 09:56 AM   #4
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According to the charts R12a ( auto ) should be replaced with R134a.
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Old 27-09-2004, 02:45 PM   #5
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You can "retrofit" an existing R12 system but you must do the following. Remove the compressor, drain the oil out, refit the compressor, rig up a run round pump to flush the mineral oil out, charge with syntetic oil, dehydrate system and recharge with R134a. Run the system for a few hours, reclaim the gas out of the system, remove a sample of oil and check the mineral content of the synt oil, if above recommended doseage, repeat the above again. You will also have to replace the filter drier twice as well as fitting R134a tap connectors over the existing 1/4" flare fittings. That is the correct way to do it and it is very labour intensive, I was retrofitting as early as 1993. The other method is to just recharge with R49 without removing the oil, this gas will work with mineral and synthetic oils and is now a good proven gas, I have used it daily in all aspects of refrigeration for years with no problems or noticable drops in performance. If you retrofit without carrying out the following you will destroy the system by blocking it up with sludge, and mineral oil and synthetic oil separates and one floats on top of the other like water on oil, I have seen many compressors destroyed by this.
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Old 27-09-2004, 06:37 PM   #6
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I also believe that by mixing R12 and R134a without following the correct evacuation procedure as described by Andy can cause over-pressurisation problems. Apparantly as the gases mix, it can cause anomylous readings on the pressure monitoring equipment, leading to damaged seals/other components as the extreme pressure tries to find an escape route!

Watch out for the cowboys who just wanna make a quick buck filling your system for 50, without checking for leaks etc first!

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Old 28-09-2004, 07:21 AM   #7
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We have air-conditioning engineers fully trained working with us now and I'm just starting to learn about it, out of curiosity really. It is amazing the bad practices employed by some of these cowboys.
As Will says just watch out for the cowboys, I've already come up against a few in the short time I've been studying it.
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Old 28-09-2004, 08:48 AM   #8
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Thanks for the help!

Thanks for your replies. R134a looks like a no-no for me. An engineer is recharging the system with a R12 replacement "drop-in" refrigerant that is happy to run with mineral oils and importantly my existing rubber seals. He might well be using R46, but I'll post back. Hopefully he will not find a significant leak.

The car has only traveled 400 miles in the last 2 years, and I can see a gas/liquid mixture flowing through the inspection glass. Lost gas has probably leaked gas past the compressor shaft seals, and fairly slowly too, considering that there is still some left. Fingers crossed an evacuation/pressure test and recharge will be all that is needed.
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Old 30-09-2004, 03:32 PM   #9
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Quote:
Originally Posted by Andy W
The other method is to just recharge with R49 without removing the oil, this gas will work with mineral and synthetic oils and is now a good proven gas,
Good news, the engineer says that due to the car being stood 2 years, the gas has leaked through the compressor shaft seal. The leak was tiny, and by using the car again it should reseal. He extracted 80g of R12 and replaced it with 990g of R49 and the a/c is cooling down to about 8C.

He suggested that I should run the a/c in the winter by at least pressing in the demist button once a week for 10 minutes.

Cost was 74 + Vat with a home visit.
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