What is the latest on the freon mixing ? I thought I had a couple of rusty R12's stashed away as my daughter drives a Ranger old enough to still use it , can't find them. Can I do the valve conversion and top it up with 132A or does it need a complete evacuation ? I seem to remember a controversy about different compressor oils when the 134A came on the market . The a/c is working, just doesn't cool at idle anymore . Not looking for a long in-depth answer , just a few pointers as I'm rusty on the whole situation.
If a seized compressor is your goal, yes. FWIW, "evacuation" is the process of pulling a deep vacuum on the AC system facilitating the removal of any moisture that may be trapped inside. Your description of the system performance suggests that there may still be a viable quantity of R-12 remaining in the system. The removal of this remaining quantity of R-12 is called "recovery." Recovery always occurs before any attempts are made at evacuation.
Controversy? R-134a doesn't carry mineral oil very well, the lack of lubrication results in a seized compressor and a contaminated system. Ester oil is carried fairly well by R-134a and co-exists fairly well with mineral oil but it is not the ideal lubricant and the added volume along -with- the existing mineral oil results in a loss of cooling efficiency. PAG oil of the proper viscosity is always the better choice, however, it does NOT co-exist well with mineral oil necessitating the complete removal of the mineral oil from the system before the installation of PAG oil.
May not be a refrigerant problem at all. I'd look first at airflow across the condenser. Is the condenser clean or is it plugged up with debris and bug carcasses? Have you measured the delta temperature between the condenser inlet and outlet? Does cooling at idle improve if the condenser is sprayed with water? Is the fan clutch working as it should?
You can't mix, it's one or the other - they operate at different pressure ranges (R-134a much higher) and require different compressor oils/ Put R-134a in an R-12 system and bad things happen to the mineral oil in the compressor, it needs to be flushed and changed to a synthetic PAG or POE oil.
If you want to change over to R-134a they have kits with the replacement seals for the compressor and adapters for the fill ports. But it is a rather involved process - you have to evacuate the system, take out the compressor to drain the oil and change all the seals, then flush out the evaporator and condenser cores and all the lines with solvent. Some cars you need to replace the cores because they aren't large enough or won't take the pressures. Some cars you need to change the metering orifice or the TXV. Mount the new compressor and fill it with the right oil. Then you have to test the oil to make sure you have the mineral oil residual down to an acceptable level around 1% max. Install a new filter-drier, evacuate and leak test, then evacuate and charge with R-134a.
But that's a long drawn out pain in the keester, so...
If the system passes a leak check and is leak-tight (or as tight as a car system can get, meaning it leaks down after 6 years or more) just get it recharged with R-12 and be done with it, it is still readily available. You pay more for the refrigerant, but you save all the time and expense of doing the conversion so it's a wash.
And by the time it needs recharging again the car will either be ready for the scrap heap and it won't matter, or ready for a proper restoration and you'll spend the money.
Thank you and thanks to the other people who replied . I guess I won't be mixing the refrigerants ! I had a vague memory of the 134A was a DuPont conspiracy or something . My daughter has been away at college and will be in town this weekend , I will have too talk with her and decide which direction to go .
No conspiracy, fact is DuPont owns the trademark "Freon" for their CFC refrigerant products including R-12, and the trademark "Suva" for their HFC refrigerant products including R-134a.
Anyone can make and sell generic refrigerants using the industry standard ID numbers, or make up their own trade name (and several chemical companies have) - but if you make or sell refrigerants and try putting the 'Freon' or 'Suva' names on the box, you'll soon have a DuPont attorney (or his Process Server) knocking on your door with the Cease & Desist order.
Excellent rundown Bruce. I do take exception with one thing, though. The seals do not need to be changed in the compressor because of compatibility issues. If it is not leaking, it will work fine with R134a as long as it is purged with the proper oil (Ester or PAG) Most R12 system compressors are leaky by now, though, due to age.
Compatibility with seals was a concern early on, but has since been found to be a non issue. It is recommended to replace the seals in all fittings, during a conversion, just due to the possibility of failure. The original seals an any R12 system are now at least 14 years old. The actual leakage of the old composition seals with R134a turned out, in practice, to be miniscule. On a properly done conversion, all connections would be opened for system flushing and accumulator/orifice replacement, and thus need to be replaced anyway.
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