Retrofitting your A/C from R12 to R134a gas.
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Good information. Few of my comments
Also Synthetic A/C Oil is avaliable, such as ERG500/1000 or SRO500, which are non hygroscopic.
Always get the system flushed as Mineral oil is not compatible with PAG and R134a gas. You might be able to mix Synthetic ERG1000 with Mineral but that does not mean go ahead and do it, get the system flushed it's better not to mix oils.
Always replace the Receiver/drier
Essential Requirements to make an R12 System R134a Compatible :
- System Evacuation to remove old gas
- System Flush to clean old oil out - Metering devices such as Expansion valves cannot be flushed through, so the evaporator has to be removed so the Expansion valve can be removed in order to properly flush the evaporator
- Receiver/Drier with X7 Dessicant - All new Reciever/driers are this type.
- Compatible Oil Type - PAG or you can use a Synthetic Type like SRO500, ERG1000
R134a Service valves are not required for compatibility, it will work without them. The reason why they were made a requirement is to try stop efforts of other gasses being put in, since gassing equipment that does not have R134a adapters will not fit on the valves.
Optional Things you can do
- Replace all O-Rings with HNBR Type, they are more resistant to leakage and warping than older NBR types. You can buy them from Ashdown Ingram. Sometimes I wonder if I pay more for the Single O-ring that they place in a massive plastic bag, or the massive plastic bag itself... But for most common sizes you can buy them in packs of 20. Old NBR O-rings work fine with R134a, but somewhat to a less extent that is probably not noticable, they may swell more but this does not mean they will degrade to buggery in minutes. If you have the time to go around the whole system (or most places reachable), they are not too hard to replace. If you are not confident doing this you will most likely bend and twist hoses while undoing them, then cry, then get a shop to do this for you. Since your o-rings might be very old and are likely to leak in the future or already have leaks, It's a good idea to just replace them to avoid any future leaks.
- Replace Hoses with Barrier Types that have a lower leakage rate. Good idea anyway if you have a 20+ Year old car.
What not to do
Pressure Testing - Controversial issue as pressure tests use upto 300 PSI on the whole system, you're very likely to create a leak in the Evaporator, that usually never see's pressures as high as that. Most gasses have a U/V die, so it's easy to spot leaks with a UV light. It takes a bit of skill to be able to spot leaks with a UV light but I was able to find all my 7 leaks in my Soarer and fix them.
Do not Mix oils that are not compatible.... If you don't know what's compatible and not, do not mix oils at all.
Do not Mix gasses e.g topping up an R12 System that is low on charge with R134a.
Do not try to be a genius and use gasses such as ones used in Air Conditioners (R-22), their operating pressures and characteristics are not suited for use in cars.
Do not be a Hero and re-use your Receiver/drier. Apart from Compatibility of your old one with the new gas there are other reasons. The old one is most likely depleted and will not be able to absorb any more moisture, could be a possibility that the moisture inside of it will now circulate your system again. Old receiver/driers have a tendency to split their bags open and circulate the tiny desiccant balls around your system, they will clog you're expansion valve. If you have one that has inlets coming from the side you can most likely replace it with a universal ones for $8. If you have one that has pipes that bend downward and connect to the top of it, you will have to buy a specific one for about $40.
Originally Posted by Howieau
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