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Old 08-18-2011, 09:40 PM   #1
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Mix R12 & R134a?

Needing to recharge AC in my '91 Lumina. What are the possible consequences of mixing the 2 rerfrigerants & their respective oils?
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Old 08-22-2011, 01:03 PM   #2
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Re: Mix R12 & R134a?

Even though the 2 types of freon have different operating properties, most do it your selfers will just dump the R134 on top of the R12.

This is a quick repair for the hot summer days. If you really want to keep the car for a long time the R12 should be removed , system purged, new oil and R134 added to system.

That being said your cost is well over $100.00 and you may still have a leak in the system so further recharge or adding R134 will be necessary.

The other side of the coin is, $10.00 for 16oz of R134, a adapter to go from R12 to R134 port and you done for awhile.

Your call.....

Just my worth.

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Old 08-29-2011, 11:09 AM   #3
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Re: Mix R12 & R134a?

The short answer is yes if you intend it to be temporary and the system is already pretty empty. If you're trying to "top it off" then you'll end up doing more damage than the benefits would give.

Now is a great time to conisder converting to R134a if the system is already nearly empty. I don't advocate releasing R12 into the atmosphere, but if the system can't hold any pressure (the pressure gauge reads zero) then the R12 has already been lost and there is a negligible amount left to recover. In this case there is a definitely a leak and you have air contamination of the system which requires a vacuum pumpdown.

If the pressure is very low but not zero (10-20 psi), then there is a small leak and a little R12 left but no air has gotten into the system. You can recharge with R134a with a leak detection dye to find the leak and repair while you do the conversion.

Because the connectors for R134a are different than the R12 ones on your car, you'll have to buy an adapter kit for about $15. These screw onto the old fittings easily. If the kit doesn't include new valve cores and the system pressure is zero then go ahead and buy them, too. Many times these are the reason for the leak.

Next, work on finding the leak by recharging with R134 and dye and run the system for a few days. Then inspect the system lines, couplings, and fittings for evidence of dye. You can replace the bad part or o-ring (you can buy a o-ring kit to replace all of them at once) and prep it for conversion.

A new accumulator is recommended since it is likely old and contains old R12 oil. These usually run $30. A small bottle of new oil should be abt $10. Pour out the oil from the old part and measure how much it is. Pour the same amount of new oil into the new acculmulator and install. Then pump down the system to a vacuum and recheck for leaks. You can borrow a vacuum pump from AZ (with sizable deposit) or buy a decent one online for about $100.

If it system holds vacuum then you can charge with R134a to the specified weight of refrigerant, usually 2-3 cans at $10 each.

Hope this helps!
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