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R-12 to R134a Posted by Gene N [Email] ![]() ![]() ![]() In Reply to: Re: Ac compressor, Everett ![]() |
You could do a search of the bulletin board for a more detailed procedure, but this is what I would consider a reasonable list:
1. Remove the old R-12. This should be done at an A/C shop for environmental reasons. However, if your system is empty, you should find out why, i.e., look for leaks in hoses, fittings, compressor seals, condensor or evaporator, and fix those before you start.
2. Flush the old mineral oil out of the system using an A/C flush or mineral spirits. If you use mineral spirits, make sure you get it all out of the components by blowing compressed air through the part you are cleaning. To get the oil out of the compressor, it requires that you dismount it, remove a plug on top, and turn the compressor upside down. Do not use flush on the compressor.
3. Replace the O-rings on any fitting you take off. Use new HBNR O-rings (green) when you replace the fitting. It is not necessary to disassemble the whole system to replace the O-rings. When you replace an O-ring, rub it with compressor oil before you reinstall the fitting. Tighten the fitting, but don't go crazy. The O-ring does the sealing, not the bolt.
4. Replace the filter/dryer. You should probably replace the expansion valve while you are at it.
5. Add new esther-based oil to the compressor (6 oz.).
6. Put new R134a style service ports on the compressor.
7. Hook up your gauge set and pump the system down with a vacuum pump for 45 minutes. The high side valve and the low side valve should be open. When you are done pumping, close the gauge valves and make sure the system hasn't leaked after 15 minutes. Open the low side valve ONLY and pump for another 15 minutes Close off the vacuum pump connection and start adding R134a. You will need 32 oz. to charge the system. After you put in about 12 oz. you can start the car and continue charging.
8. Check the pressures once you have added all of the R134a. The low side should be around 30 psi and the high side depends on the outside temperature. I have a chart I use, but I have seen a formula used to determine the working temperature. It is something like 2.9 times the temperature (in Fahrenheit), so a 90 degree day would yield 260 PSI, which seems about right.
Robert Kaplan (aka, Kappy) has a pretty detailed write up on this in past postings, but this should give you a general idea.
The key here is attention to details and having the proper tools. Access to the proper tools is a must. You are going to need a gauge set, a vacuum pump, and some way of flushing the system. Also, a leak detector would be handy.
posted by 155.104.23...
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