A/C switchover
 

Hey everyone hope life is treating you kindly. I have a 93 1 ton that the air finally quit on me. I plan to switch it to 134a refrigerant and need to know what all I need to change to over to use the 134a. Thank you for your help.

You need to flush the system as best you can of the mineral oil and use PAG or ester oil instead. I switched to 134a but I haven't been happy with it since. I found some reclaimed R-12 on fleabay so I plan to switch back. There is a thread in the sticky's telling how to do the conversion. I also added a pair of electric fans to the front of the condenser to give better cooling in stop/go traffic. You should be able to buy everything you need at O'Reilly Auto. It's probably a good idea to replace the dryer and expansion valve while you're at it. Everything can be had for under $100 usually. The compressor is more expensive if that needs replacing. Get a set of gauges and a vacuum pump to evacuate the air before you charge it. You can't put as much R-134a as the system holds of R-12 without popping the high pressure relief which goes at 600 psi. 80% R-134 IIRC is the amount. The glass on the drier will still show bubbles so don't try to fill it that much or the pressure valve will pop. If you pop the valve you'll lose your oil all over the bottom of everything and it's a mess. It takes 8 ounces of ester or pag oil. DO NOT USE Mineral oil for R-134a.

Edwin

thank you for the information, it is much appreciated.

In addition to Edwin, i took the system apart and flushed it with cheap brake clean, dries faster, and compressed air.
20 years later, still going.

When I worked as a mechanic years ago,I bought cases of 70% denatured alcohol in pint bottles at the drugstore when they went on sale 49 cents...I used a bottle per flush with compressed air, and never had a complaint...[whistle]...Ben

I just bought the EPA approved stuff in the spray can at O'Reilly's. Not that I give a crap about the EPA but because I didn't know of an alternative. Alcohol is cheap but the spray can may be more convenient for some. Live and learn. Thanks.