I just had someone over too look at our AC units, and started to talk to him. Told him about just converting the R12 AC in my 72 over to R134.

He said he wished I hadn't already, that I could have just gotted R420a instead - said it's cheap and a direct replacement for R12, therefore no need to change anything, just need to have the old R12 removed and replaced with r420a.

Anyone else use 420a?

 

Why don't you just recharge it with R12? It's available and was designed to work properly with your system. You won't have to flush out your system or change anything.

If you do a search on it you'll find that it's an R134 clone. I'd stick with what works.

 

134 here, some 15 years ago, with all new O rings, and valves, and a '88 up vette serp drive/compressor.....

adjust the POA valve stem in the top of it, about 1/2 turn counter clock wise, with the nut loose, then adjust it snug again....

simple as hell, that adjustment is courtesy of ZWEDE here in the forum, and I finally got around to doing it after some 6 years I leaked enough 134 to make it worth doing.....

freeze the ***** off a brass monkey now....

 

I plan on rebuilding my A/C in my '79 to R134a. I think it's the way to go but you should do everything at once including hoses and o-rings, dryer/accumulator, compressor, POA valve and flush the system entirely. Then evacuate the system for half to an hour, then fill with R134a. I got the vacuum pump and gauges in a kit on ebay for about $50.

Here is some CF info that might help. See attachments

http://www.corvetteforum.net/c3/zwed...e/ac/tools.htm


Here is a post from a refrigerant forum that you might find interesting.

What you have described is just freeze 12 with 1% of the R134a removed, and 1% of the R142 removed and an “extra” 2% of oil added. As with all blends, and they all work, you have a fractionating refrigerant. The first to leak out will be the 142, leaving R134a So why not properly retrofit to R134a?? Blends need to be charged as liquid so the “mix” stays intact. That also means they can’t be topped off, as one leaks out faster. So every time you need a top off, you will need to recover and charge from scratch. Also, 20hg vacuum is not enough, unless you’re at 9,000 ft above sea level. “ANY” moisture left in the system will mix with the R134a and form hydrofluoric acid, which will eat the system from the inside out..You will not find many repair shops to service your system, and will be hard pressed to find all the service equipment like service ports,, hose adapters etc. in most ac shops. It would be near impossible for shops to keep them all for the many “alternative” refrigerants out there,(all of which claim theirs to be the best) and there are many.. So ac shops in general service two refrigerants. R12 and R134a. Shade tree mechanics can use anything they like in their systems, but please label it properly (EPA law) so that AC techs will not ruin their recovered supply of R12 with a blend which will make their refrigerants as worthless as the blend is..Blends work best in stationary equipment where leaking is not a problem as it is in MV use..There is no need to use anything but R12 or R134a. they are both readily available, do not fractionate, can be topped off and can be serviced by any and all Ac shops. Also, they don’t void
warranties.. blends do..Just my two cents..

BTW...Alternative refrigerants have been discussed here for years..Never changed the thinking of AC techs yet...

 

In the grand scheme of things R12 is not much more expensive than R134. And it works.

 

I agree with you that R12 is better if your system was originally designed to use it and it has a lower head pressure than r134 which causes less stress on your system plus you don't have to do all the modification for conversion. However, if you are certified to purchase refrigerant, R12 is over $20 a pound and 134 is about $3 a pound. But, I guess you qualified that by stating "in the grand scheme of things". $50 for refrigernant would be cheaper than converting to 134.