How to: Converting an R-12 Air Conditioner to use R-134a

[UserName]

I converted my A/C with the $30 kit 2 years ago. Took 15 minutes with no tools. Changing the air filter is more involved.

 

[saxdaddy]

Well, I had a similar experience...My cousin is a mechanic licensed in a/c repair...I took my Ranger to him last year for conversion..Fellows, lemme tell you, it's not exactly cheap!! There was zero charge in the system, so he disassembled the system, flushed lines, replaced reciever/dryer, orfice and used ester oil for the recharge.
It has been a very worthwhile investment as a year later it will still make you shiver!! I'm getting ready to haul my 92 Explorer Sport in for the conversion as well...I'll be thanking myself soon enough as July nears!!

 

[Glacier991]

Sax that was a good job then I'm sure. It will last you a good while. Congrats for having it done that way and springing for the bucks now, rather than a system replacement in a few years.

happy exploring


Chris

 

[Glacier991]

No offense meant to anyone.

 

[silver stripe]

hello to all
just thought i would let you know that i converted my system over like 3 years ago, myself // i use to do ac work at a local rad shop // so i had all the tools // there was a stink before about having to change the dryer, oil, orfice tube compresser ect........... not likley, i evacuated the system, pulled the line off of the dryer, added 3 oz of the new 134A oil to the system, along with the old R12 stuff, put it together again, changed the fittings, vacummed the system, then when i got a good reading from the vaccume, i put the 134A freon in, but the secret is to read off eather the evaprater box, sometimes on the dryer, the old R12 amout of freon needed, and drop a 1/4 lb of freon.

try it you will be impressed, revving my truck at normal driveing rpm's (1500), the system will blow out 6 degrees, and i have not touched it since this year when i checked that i lost no freon over the winter.

 

[Glacier991]

I ran into a situation recently that made me think I should have mentioned something important but didn't. Valve CAPS !

Believe it or not... the valves are a common leak point, especially in 134 systems since the molecules are smaller and leak out more readily. Often we see caps as just "dust covers" but they are actually part of the system sealing defense. If yours are absent, get new ones and put them on. Lube the inner rubber seal with mineral oil if you have it. I can't tell you how often I remove a cap and hear a slight hiss.... it was doing it's job. Just an afterthought.

Cool Exploring


Chris

ps. equally true on older pre 95-96 R-12 systems !

 

[Alpha_Geek]

Just a quick note about units of measurement and vacuum:

mm means millimeters, microns are typically represented my a lowercase "u"

When expressing vacuum or pressure in "x" mm HG, what that means is "This vacuum is strong enough to pick up a column of mercury that's "x" tall?

If you'd like a peek at a handy dandy conversion chart in order to get to psi, gm/cm^2, etc etc, etc, the nice precision measuring equipment folks have just the web page for you!

http://www.pmel.org/HandBook/HBpage25.htm

Regards,

A_G, former Florida Army National Guard 35H (Calibration Specialist)

 

[Glacier991]

Alpha... thanks, good post. did a photo post of a recharge on a rebuilt system, thought it ought to have a link here, so here it is:


http://www.explorerforum.com/forums/showthread.php?threadid=84675&referrerid=15286

Happy and Cool Exploring to all

Chris

 

[Peter]

yeh...i tried the conversion kit, lost 20 oz of r134 OVERNIGHT...and all that money and ozone destroying stuff was out completely...so i figured i had a leak, put in some with the dye in it and used a black light, couldnt find a leak and that coolant lasted for a couple more days (almost as if the stopleak did its job) and now I either dont have enough pressure in the system to make the compressor kick in, or it leaked out...though I have a small amount of pressure in the high pressure side......but the moral of the story is (in my opinion) those conversion kits are junk, and AC is enough of a specialized system (like a tranny) that if you dont have the time and energy and means to retrofit and AC system THE RIGHT WAY its not worth the time and im going to take it to guys that do it all the time cause I gave up

 

[Glacier991]

It's that time of year again (bump)

 

[F14CRAZY]

Ha! Thanks to my dad, there's a surplus of about a dozen R12 cans out in the barn that he picked up form Car Quest like right when it was made illegal. I'm sure it'll come in handy someday. (Las, I think I have factory R134a, I'll check again)

 

[adale]

Switches

My '93 Navajo is needing the R134a upgrade. I looked at the pressure switch and there is no adj. Do I need to change out the switche(s). Thanks and great posts everybody. This is what these forums should be but seldom are.

 

[Glacier991]

Adale... you can convert without any changes. The only recommended change is generally to add a high pressure cutout for 134a. If I recall this cuts out when head pressures reach 440 pounds. I think FORD has a retrofit, and Classic Tool Design has their own add on as well. I've done conversions where I have not changed a thing....and candidly, an adjustable low cutout is a recipe for people to fool around and end up with frozen evaporators. The non-adjustable is fine. On another note, there is a variable orifice expansion valve on the market. I had stayed away but may be a guinea pig to see if it works as advertised. It might be a fun "exploration". I'd definitely check or change the expansion valve on the changeover.

 

[adale]

You're a prince Glacier. So you are saying to change the expansion valve? To what? Is there a specific one for R134a?

 

[Glacier991]

The expansion valve (actually it is an ofifice tube, and I tend to call it an expansion valve - same function - see note in the following post) for the old R-12 will work fine with R-134a, but you pose a good question I have not researched - IS there enough difference to warrant a different expansion valve? I'll check and post what I find. My caution was just to make sure it was clean and free of any debris.

 

[adale]

Expansion valve and hi pressure cut off

Glacier, are you referring to the orfice tube as the expansion valve? Also where do you mount the high pressure cut off switch ?

 

[Glacier991]

Yes I am using those terms interchangeably. As for the hi pressure cutout, the version you get will instruct you where to mount it.

 

[adale]

R12 to R134a change out

Finally completed this! Wasn't real hard just time consuming and getting to some of the fitting, like were the orfice tube is, was a real PITA! A couple words of caution, be careful when putting the R12 to R134a adapters on the manifold hose, it will break easily, don't ask, and yes it was expensive. Also be sure to pull a vacuum at least one hour, possibly more if it is a humid day. Also there have been a lot of posts about the vacuum measurements when doing this. Remember you really are evacuating the system not simply vacuuming it out, that is why you measure the vacuum in microns and not inHg. BTW on a 75 deg day, with 80%+ humidity, my system now puts out 39 to 40 degree at idle and makes a really big puddle of water quickly. I drove it to work today, and it is supposed to be 70 deg, so we will see what happens!
Thanks to all and a special thanks to Glacier your posts and insight saved me big $$$ and I am sure a bigger head ache.

 

[Glacier991]

Glad to hear you pulled it off. Happy I was able to help. This is how I see this forum excelling... sharing what we collectively know.

 

[sajnaj]

ok do u have to chnage the oil if u swtich to 134a i have heard dif things