R-12 to 134-a Change-over

[chengny]

Anyone done this procedure?

I maintain and drive a real nice 86 K2500 (un-airconditioned). Recently came across a posting on craigslist for an entire OEM A/C system ($50).

My truck is stock and I truly intend to keep it that way. The package includes everything I need to install factory air conditioning. I would really rather not mess with the truck more than necessary but that OEM A/C sure would feel nice during the summer. Saves a little gas on the highway too, so they say. It would be a shame to scrap this set-up.

I have a universal refrigeration license and access to sufficient quantities of R-12 and I could go that route, but am leaning toward switching over to 134-a.

I'm sure that you can understand that there will be some refrigerant loss during the initial install and the subsequent de-bugging process. I'm cheap and R-12 isn't - so 134-a would be a better choice as regards $. But if the system is designed for R-12 and I do the job right the first time I could live with that.

So anyway... ideas, suggestions, opinions, advice, I'm open to it all.

[gmctrucks]

That's a good price R-134a would be the cheapest way to go. My brother is having a Rat Rod/Hot Rod built I say both names because it has a chopped top but it will have windows that roll up and A/C I think it's going to be placed in the trunk I know it's just for these types of cars or kit cars.

[03chevy]

the conversion is easy to do. first thing to do is replace every O-RING on all the lines. then hook up the system, and after the you will need to have a vaccum pump to get all the air out of the system. if not you can go to a a/c shop and have them vac. it down for you. then go home with the r134a kit you got from a parts store has everything you need. and follow the directions just as they say. it is easy to do i have done almost 100 kits or so.

[chengny]

Roger that 03chevy,

So no replacement of components is reqiured, just o-rings, correct? What about the compressor seal? I would imagine that it is good engineering practice to replace that at the time of conversion - is th seal for 134a composed of different materials? Or should I just forget about using the old unit, bite the bullet, and buy a new/re-built comp?

I have a decent Robinair vacuum pump and can exacuate to over 28.5" Hg with that. Intention is to leave it on the system for a couple of days - on for 4 hours/off for 4 hours - due to the age of the system and the manner in which in was stored. It's been open to atmosphere for a few years and I'm sure it is loaded with moisture and non-condensables.

I will also install a drier (I'd love to find a couple of valves to isolate it) and blow out as much of the old oil as I can.

I can dial-in the charge with gauges and a chart well enough, but does anyone know how much refrigeration oil it requires?

[shortcut]

This is great to know as I am in the middle of restoring an 84 silverado with factory air,and everything is still on the truck.I had no idea it was that simple to change to 134-a. Great Post

[chengny]

Looks simple so far doesn't it? I betcha that the devil will be in the details on this one. See my commment about purging any residual oil (I actually plan to flush/pickle the piping and components).

I think, from what I have been able to read, that this is one of the easiest refrigerant conversions one can do. Apparently 134a into a former R-12 system is as close to a "drop in" as you can get.

It seems that the biggest change is the addition of larger "Schraeder" valves - to enable your gauges to attach to the piping. It is also becoming apparent that the conversion kit is just that - a set of ported valves designed to fit the newer hoses and some refrigerant. But don't forget about the oil.

If you have exposed your system to the atmosphere for any length of time, the oil quickly becomes contaminated with moisture. This entrained moisture will boil off and cause problems once the system is activated.It is important to flush and renew the system with the proper quantity of oil (of the correct viscosity).

[Chevy_Finatic79]

Just to throw it out there. Having the windows up and A/C on consumes fuel quicker and you get less MPG -VS- having the windows down and the A/C off "the Drag factor theroy" was debunked on Mythbusters they had two identical ford explorers with exactly the same amount of fuel. they both drove around the track until it ran out of gas. the explorer with A/C off & windows down went 30 miles longer than the other one with the A/c on & windows up.

I'm a big fan of A/C and dont really care if it robs gas mileage I like to feel "Cool" when I'm driving in the 100+ summer days here in Nebraska.

I did the R134 retro-fit kit on one of my vehicles along time ago and I didnt get my system flushed or vaccumed I just cracked the line let the R-12 blow out and replaced the orings and filled it back up with R134 and it blew at 42 degrees for 5 years after that problem free. I didnt know you had to get that much stuff done to the system before refilling it. I do know I wasnt supossed to release the R-12 but I was younger and dumber.

[03chevy]

chengny one kit should do one truck or car and no new comp is needed

[junior3382]

This will show my personal inexperience in the finer things in life...lol... But for my personal knowledge and for the record, I assume you are talking about different types of freeon with the reference to R-12 or R-134-a right? If not, what are they, and what is the differences between them? I can keep up with mechanical knowledge and even some electrical, but refridgeration and cooling is a not something I know a lot about. So forgive the question, but I was curious.

[03chevy]

Differences between R12 and R134a

One of the differences between R-134a and R-12 is the boiling points. Pure R-12 will boil at -22 degrees Fahrenheit while R-134a boils at -16 degrees Fahrenheit. If we hooked up a gauge to a bottle of R-12 refrigerant which contains liquid, we would have about 117 PSI at 100 degrees F. The pressure of reading of R-134a at that same temperature would be about 124 PSI. For this simple fact, R134a gauge readings will be a little different as compared to R12. While the overall temperature curve is different and the critical temperature is lower, during most operating conditions, you'll find R-134a is a fairly close match to R12. R-134a is slightly less efficient and condensers will usually have to be upgraded to match the cooling performance of R12.


Another difference is the the type of lubrication that will required when using R-134a. For years, most R12 compressors required a standard 525 SUS viscosity mineral oil. Mineral oil will not mix well with R-134a. They seem to coexist just fine, but, since mineral oil is not miscible with R-134a, you'll need to use a suitable oil. PAG oil is what most OEM's recommend for use with R-134a in automotive systems.


There are also political, economic, and safety considerations between the two chemicals which remain outside the scope of this basic informational article.
For more information on R-134a, please visit the following sites:
Genetron Refrigerants
DuPont Refrigerants
U.S. EPA: Guidance on Retrofitting to HFC-134a