DaleClark

iTrader: (55)

They did change the material the O-rings are made of to be compatible with 134a and the newer compressor oil. But, if you buy any new O-rings, you'll most likely only be able to get the 134a-compatible-material O-rings.

That said, if an O-ring is still working, it will probably keep working with 134a. But, IMHO it's a good idea to take care of ALL the O-rings if you're doing some major AC system work, as they're a very frequent failure point.

Dale

DamonB

There are in fact different o-rings for 134a systems but it's not because of the freon, it's because of the oil. R12 and R134a systems use different oils and R12 oil is not compatible with 134a oil. When I converted my system I did exactly as DaleClark describes. I removed all the old freon and also drained the drier and the compressor of their oil. I replaced every o-ring in the system with a new one that is compatible with the new 134a oil. R12 oil becomes acidic in the presence of 134a and its oil so then it eats your o-rings and compressor seals over time. Again this happens over time and combined with people over charging with 134a leads to the "I converted and it worked great for a while and then crapped out" stories.

There are two types of oil IIRC correctly: ester and PAG oil. I forget which goes with which system but my understanding from the great a/c shop I found was that you could run r12 oil with r134a seals but you couldn't run r134a oil with r12 seals as it would eat them. The new o-rings I installed for the r134a conversion happen to be green rather than black. I don't know if that's a way of telling them apart or not.

The "conversion kit" I used was nothing more than the commonly available adapters for the high and low side ports. On top of that I drained all the oil from the system (it sits in the compressor and drier when the system if off), replaced ALL the o-rings with 134a types, pulled a vac to check for leaks and then added the r134a oil. I then pulled another vac and charged the system. My 130,000+ mile compressor is wearing out because even when charged correctly the high side reads a little low and the low side reads a little high. The seals are wearing so its pumping efficiency is going down. I got a steal on a new compressor long ago but haven't added it yet. I'll do that soon and switch back to r12 most likely.

mad_7tist

you are right about the oil. it does turn into black goo when it is exposed to moisture/air for any length of time. i think it is crazy to tell people they need to change the o-rings because the refrigerant is different. they are 10 years old so do it.. ok maybe. if you flush out the condensor and evap. replace the drier (all of which should get done) you need to put new orings on those components. an overwhelming percentage of ac problems are component failures. on r12 systems the schraders leak. and on cars that have them the crimped flexable lines they fail. o-ring problems are usually installer error wrong o-ring it was pinched etc.
damon have you give any thought to your expansion valve not functiong properly? ester is the old stuff pag is new. the ase says that the incompatibilty of the 2 is that mineral oil will not move through the system with 134 well enough to keep the pump properly lubricated.

Speed of light

iTrader: (8)

Guys, There is a lot of misinformation and half-truths contained in this thread. So I'm going to chime in here on with factual information on a few of the points, drawing from my engineering design experience with refrigeration systems.

Probably the best thing to do IMO (for most of you), if the $$ is reasonable, is to recharge your R12 system with R12. Most of the shops doing this use refrigerant that has been recovered from other systems. There are alternative refrigerants of several different types that also could be used with good results, but some research must be done to insure materials compatibility with the a/c system. (With the exception of HC12a, which is a drop-in and will work fine in any system--period.)

I would, under no circumstances, convert to R134a. It is a very poor refrigerant (relatively speaking) and doesn't do anything very well. R134a exists as a political solution to appease the companies that produced the problematic R12, which formerly made them very wealthy.

1) Mineral oil used in R12 systems is not miscible with R134a and MUST be changed to a POE or PAG type oil, which are not very good lubricants and are very hygroscopic. Ignoring this point will result in compressor failure;

2) R134a is a much smaller molecule than R12 and requires system changes, such as barrier hoses to prevent it from leaking out. It will find all the leaks you never thought you had in an R12 system;

3) R134a is very flammable--even more so than propane--and produces toxic products when combusted. You guys that are concerned about propane should check out the ignition temperatures and the LEL's for R134. How R134a was classified as non-combustible took an act of Congress--literally;

4) R134a is considerably less efficient than R12: has poor pull down performance, and operates with higher head pressures (another potential compressor failure point and larger power drain on engine).

Sorry, R134a is just a lousy refrigerant for a lot of reasons.

Additionally, pure propane is not recommended, as it is not well matched to the R12 refrigeration cycle; however, a good HC substitute is 50% R290 (propane) and 50% R600 (isobutane), aka HC12a or equivalant. Its enthalpy characteristics are very close to R12, it has a large molecule, no materials or oil compatibility problems, it's more efficient, it's cheap and easy to use.

BEFORE recharging the system with any refrigerant, I cannot overstress the importance of getting all of the air and moisture out of the a/c system. In order to do that effectively, you need a high vacuum. At room temperature that means at least 29.25" of Hg to flash out all of the moisture. Anything less will really not get the job done. A 28" vacuum, for example, will only remove 94% of the air. Air cannot be condensed in an A/C system and will get trapped at the top of the condensor resulting in loss of efficiency and higher than normal compressor discharge pressures.

Hope this helps....

tzbfwt

iTrader: (1)

So Dave

how safe do you feel with R134A in your system now??

thanks Speed of Light - very informative Post , but where the heck do I get my hands on some H12a?

any truth to the rumor that R12 was phased out because Dupont's patent rights ran out and it had to come up with some new gas to patent?

widebody2

Wow this thread has got a lot of info in it. I'm going to keep it as simple as possible. I'm going with the r12 and will be having the shop do absolutely everything besides putting it together. No pumps, no propane haha. I doubt its going to work anyway to be honest since the condenser will be getting terrible flow. The fan on the condenser was a good idea, which I had looked ta doing previously but there's no room for that either. Most likely I'll get it recharged, it won't work , and it'll end up in the basement. I actually put together a misting system for it, but that was more for fun...I don't think that'll get the job done either. We'll see.

DaleClark

iTrader: (55)

Don't forget, with the stock cooling fan system the fans will always run at low with the AC on. This is supposed to help pull air through the condensor and radiator to improve AC performance when the car is stopped.

Dale

dgeesaman

iTrader: (7)

Considering that the R134a in my dd is designed that way, no problem. My R2 takes R12.

But compressing flammable gases because someone said it might work is still pretty stupid. If you can't explain why it's safe, you're taking someone's word for it.

Dave

iluvmy3rdgen

This is why I suggested a fan on the condensor.

widebody2

won't fit unfortunately

iluvmy3rdgen

Was the undertray in the way? Can you fit the condensor between the fans and the radiator?

Speed of light

iTrader: (8)

Originally posted by tzbfwt:
No, I don't think so. At least it didn't start that way. R12 was in production since the '30's and was a highly profitable mature product for the few companies in the business of synthesizing it. However, CFC's, the class of refrigerants that includes R12, does have a real problem with the ozone layer. The short story is this that CFC's can migrate to the upper atmosphere where its chlorine reacts with the ozone to form new compounds and thus depleting the ozone in the process.

I think the real story is the undeserved preference that was given to R134a, a marginal and inferior product by most accounts. It became the defacto standard in a very guarded deal between politicians and the interests representing R12. Think about it. The government banned their product so they had to make a major concession to the chemical companies to compensate them. It is widely believed that this was done by advancing R134a, another difficult to produce synthesized product that the chemical interests held patents and licensing rights to. So by all accounts the chemical interests did very well. Unfortunately, the rest of us got a refrigerant that is very inefficient and very problematic--shoved up our ***--to be quite candid. What I'd like to know just how well the bureaucrats and politicians did.... Did they switch to a POE based lubricant on their backsides'?

Alternative refrigerants are out there and available from many sources albeit you need a refrigerant license to buy most of them. (They are also EPA legal if properly implemented). They can be used to replace, retrofit and upgrade systems. Unfortunately, a lot of shops will not tell you this because they just don't want to learn, invest and/or handle alternative refrigerants. Yes, you can improve the performance of your 134a system!

IMO, the major factor in deciding what to use comes down to what has to be done to the system to accommodate it. Your requirements will vary.

For those still into fluorocarbons, HCFC blends are available (R414b) that will do a very good job--even better than R12--but will require some retrofitting of hoses and seals in some (usually older) systems to prevent the R22 component of the blend from leaking out and causing fractionation.

HFC (R134a) fans have several blended refrigerants (e.g., Freeze 12) available that offer improved performance, especially in systems that already have POE/PAG oils in them. If you have a stock or converted R134 system, you can easily get improved performance by using HFC blend. I still would not recommend them for R12 conversions--which is contrary to their manufacturers' claims.

If you're willing to use an HC (hydrocarbon, aka organic) try enviro-safe at es-refrigerants.com (es12a), hychill.com (hc12a), autorefrigerants.com distributes these and there are many others. If you can get over the phobia that you a/c is gonna blow up with an HC then this stuff is almost too good to be true. This is why it is widely used in other countries where efficiency is important and the chemical companies don't control the legislatures.

Originally posted by widebody2:
True, you cannot move heat out of the refrigerant without some condensing airflow. Surprisingly, your misting set-up may help quite a bit under marginal conditions--especially if you're in a dry area. Recommendation: Find some way to improve airflow over the condenser. Use of blended refrigerant may help as well as it spreads the heat load over a larger area of the condenser.

A couple of other things:

I saw some debate about this, but be advised that refrigerants are not inert; they do react with system and sealing materials, and some oils can attack certain seals as well. So you do have to pay attention to this. This is what makes conversions such a cluster****. If you can do a conversion with a refrigerant that uses mineral or AB oil, you are much better off. It offers much better lubricity and it is much less sensitive to moisture (hygroscopic) than POE/PAG oils.

Good luck!

BlueRex

That's some great info Speed of light.

Just out of curiousity do you happen to know how environmentally friendly the HC12a refrigerant is?

iluvmy3rdgen

You drive a rotary, nothing is enviroment friendly about that

tzbfwt

iTrader: (1)

>>You drive a rotary, nothing is enviroment friendly about that <<

AMEN - Fellow Green House Gas Emitter !!

Speed of Light - you really buy that Ozone layer eating story about CFCs??

last article I remember said that we haven't been taking data long enough to know what the real trend is - kinda like global warming

that said - I think I'll buy that beach front condo in Denver...

Nice knowing ya, all your Liberal Left Coasties !!

and can you buy the HC-based stuff from the websites you mentioned without an AC license?

thanks for all the info

BlueRex

Really, because my car still passes CA smog requirements with flying colors (for lack of a better term).

Here we go with the liberal CA hippie BS...

CFC's and there effects are a fact. The scientist Sherwood Rowland is a professor at the University of California Irvine. Him and Mario Molina won the nobel prize (atleast a portion of it) for chemistry in 1995 concerning there studies of ozone formation and decomposition, particularilly for there discovery of ozone depletion caused by chlorofluorocarbons(CFCs).

But the concensus on this board seems to be that it's cool to pollute the atmosphere if it gives you 5 extra horsepower so I'm sure someone will have a smart *** comment about this.

iluvmy3rdgen

So just because you pass a test that lets your car polute the earth to a "smaller degree" (for lack of a better term) then a car that has more polutants makes it environment friendly? Think again buster.