To Change-Out AC Refrigerant, or Not?

[Elliott P.]

What really should be done to affect change-over (1965 Corvette example):

• Find any gas leaks in the A/C system and repair
• Replace dryer recommended (difficult to properly flush)
• Replace expansion valve with new replacement GM unit that is balanced with R134a
• Replace all

And if you already have all your Flight Awards and no longer care about NCRS Judging deductions, then the icing on the cake would have been to change out the old GM A6 compressor for a new Sanden-style compressor (with mounting kit), and a puller electric cooling fan for those HOT August Nights parades, and maybe add a newer multipath condenser to maximize cooling.

Forsooth, there be some good news here for those caught yet in the midst of a restoration. The Santech HNBR green O-rings are compatible with both R12 and R134a, and are compatible with the different lubes used with these two refrigerants. So you may start with the Santech HNBR and be in the green when you decide to change over later. Alas, Green is not always green. Since there are no official standards for these material colors, and may vary from one manufacturer to another, make sure that you are getting Santech HNBR, which they color green.

Critique and knowledgeable comments will be appreciated, since I have strived to make this as complete and as correct as possible.

[Joe L.]

Re: To Change-Out AC Refrigerant, or Not?

I have a 1965 Corvette coupe with AC; should one change over to newer R134a refrigerant, or maintain the original, NCRS-blessed, atmosphere-destroying, uber-expensive (no longer legally produced), R12 refrigerant? That is the question. And, aye, there’s the rub.

The long story, as best I can put together from several internet sources (yeh, it is what it is) and phone calls, to do a proper job:

What really should be done to affect change-over (1965 Corvette example):

• Find any gas leaks in the A/C system and repair
• Replace dryer recommended (difficult to properly flush)
• Replace expansion valve with new replacement GM unit that is balanced with R134a
• Replace all system ‘O’ Rings (including sight-glass) with new Santech HNBR (green) material for more permeable R134a gas to minimize slow leakage
• All new rubber hoses may be in order, particularly if old and brittle
• Flush system with a compound of Hydrochlorofluorocarbon-141B and Dichlorofluoroethane, which cleans and dries the old oil residue, moisture, and any other junk that may be in the system
• Install new gas input and output stems (the real NCRS judging tell). This prevents R12 being mixed with the R134a gas in the future
• Completely evacuate the system
• Load the new ester oil into the A/C system. This is compatible with the new R134a gas
• Load the new R134a gas into the A/C system
• Change the A/C system pressure & timing settings to accommodate the new R134a gas (recalibrate STV valve)
• Place a retrofit sticker on the A/C system stating it was converted to R134a usage (NCRS no-no)

And if you already have all your Flight Awards and no longer care about NCRS Judging deductions, then the icing on the cake would have been to change out the old GM A6 compressor for a new Sanden-style compressor (with mounting kit), and a puller electric cooling fan for those HOT August Nights parades, and maybe add a newer multipath condenser to maximize cooling.

Forsooth, there be some good news here for those caught yet in the midst of a restoration. The Santech HNBR green O-rings are compatible with both R12 and R134a, and are compatible with the different lubes used with these two refrigerants. So you may start with the Santech HNBR and be in the green when you decide to change over later. Alas, Green is not always green. Since there are no official standards for these material colors, and may vary from one manufacturer to another, make sure that you are getting Santech HNBR, which they color green.

Critique and knowledgeable comments will be appreciated, since I have strived to make this as complete and as correct as possible.

Elliott-------


I would not even consider a change over for any 63-82 Corvette. R-12 is still easily available and can be obtained for a not outrageous cost. It's not inexpensive but it's certainly not off-the-chart expensive. Plus, even with an empty system you don't really need all that much. As long as your system is in good shape with all seals and compressor in first rate condition, you'll probably be set for the duration. So, why dink around with a conversion. However, if your system in not in good shape or in questionable condition, I'd get that right first.

As time goes on I think you're actually going to see the price of R-12 come down. That's because there are going to be fewer and fewer cars that use it. Even now, it's been about 25 years since cars were manufactured that used R-12 in their A/C systems. How many 25+ year old cars do you see out there running around even now? And, for the most part, those that are out there now are going to be "dropping like flies", except, of course, collector cars.

[Harry S.]

Re: To Change-Out AC Refrigerant, or Not?

My understanding there is possibly some information about R12 we should look into. the patent on R12 was to expire so R134 was the new better refrigerant. Well R134 turns out to be worse than R12. The EU has essentially banned R134 and has approved R1234YF. I believe the change from R12 to R134 had everything to do with money and nothing to do with the quality or safety of the product.

Saying that I changed my 63 to R134. Well that last one summer and I rebulit the system and went back to R12. R12 in a good system, as Joe points out, will essentially last forever. As from a cooling standpoint R12 always blows at 20 degrees below ambient when R134 never cooled the car. I suggest you stay with the R12. I picked up a 30 lb tank for $275.00 and I still have 23 pounts left.

[Gary J.]

Re: To Change-Out AC Refrigerant, or Not?

You may want to have your compressor rebuilt if you are going through everything, I would, Also your original dryer can be rebuilt if you want to keep the original one.

[Patrick H.]

Re: To Change-Out AC Refrigerant, or Not?

According to my local service techs, R12 and R134 are around the same price in today's market. As long as your techs have the R12 equipment you are far better off using that as your refrigerant. And, you save the expense of switching everything in your list.

[Larry M.]

Re: To Change-Out AC Refrigerant, or Not?

You may want to have your compressor rebuilt if you are going through everything, I would, Also your original dryer can be rebuilt if you want to keep the original one.

Early driers used a desiccant specific to R12. After about 1990 or so, all driers (including rebuilt) used a desiccant that is okay for both R12 and R134a.

OP needs to replace drier regardless (due to age and service life)...........but also make sure the desiccant he uses is the latest one good for either/both refrigerants.

Larry

[Dick W.]

Re: To Change-Out AC Refrigerant, or Not?

According to my local service techs, R12 and R134 are around the same price in today's market. As long as your techs have the R12 equipment you are far better off using that as your refrigerant. And, you save the expense of switching everything in your list.

I can purchase R-134-a locally in 12 oz cans for less than $15.00. Last 30# cylinder I bought of R-134-a cost me a little over $100.00. I checked on the price a couple of weeks ago and it has gone to $120 and change. You can buy the cans without a license, the cylinders you have to have a MACS license to purchase

[Elliott P.]

Re: To Change-Out AC Refrigerant, or Not?

Thanks Gary and Larry. Your points made me do some more research. I will replace second bullet with:

• Receiver/Dryer must be replaced or professionally rebuilt, either way, using a high quality Zeolite XH-7 (synthetic molecular sieve) desiccant which will be compatible with either R12 or R134a and either lubricant. A replacement dryer will likely not exactly match the original (see A.I.M.) and be subject to NCRS deductions.

[Larry M.]

Re: To Change-Out AC Refrigerant, or Not?

If you have an original drier, it can be rebuilt with new desiccant. You can also buy original rebuilt driers with new desiccant. PaceCar Jeff (Ebay) is one source.

The rest of your statements are known information for guys that deal with AC systems........but perhaps new for you.

I believe the desiccant in a new drier is good for about 1-2 teaspoons of free water.

Ester oil can be used for either R12 or R134a. It is not the ideal lubricant, but it can be used for both refrigerants. For R12 only, the lubricant is a special mineral oil. For R134a only, it it PAG lubricant.

I normally recommend that after rebuilding a automotive AC system, an old drier or a cheap drier is installed until all pressure testing and leak fixing is complete and the system holds vacuum overnight. THEN remove the old drier and add the new drier (with 1 oz of oil) and pull another vacuum. Then begin refrigerant charging.

This keeps the new drier dry and safe and secure until the final steps.

Larry

[Brad Hillhouse (37766)]

Re: To Change-Out AC Refrigerant, or Not?

I can purchase R-134-a locally in 12 oz cans for less than $15.00.

Walmart has 12 oz cans of R134 for $4 bucks. no license, no limit. Cheaper than Pep boys or Oriellys by far.

Brad Hillhouse

[Mark E.]

Re: To Change-Out AC Refrigerant, or Not?

Elliott,

Are you asking because the AC in your '65 isn't working? If it is, leave it alone. That's more environmentally friendly than consuming a bunch of new parts.

If it doesn't work or you need to open it up for some reason, I would still lean towards R12. It's easy to get, works better, leaves the system looking original, and avoids the conversion costs.

I'd also stay with the original compressor. Properly set up, it's reliable and preserves the originality of the car. Reach out to fellow member Dom if you need it restored.

[Elliott P.]

Re: To Change-Out AC Refrigerant, or Not?

Thanks again Larry, you sound like a conscientious expert on AC and know what you are doing. I am not an expert, but I am a mechanical engineer and I started considering this change-over a year ago. I wanted to know what was needed so I started surfing the internet. As you may well know, the internet is loaded with crap. There are YouTube videos and various articles on doing this change-over for older cars by people representing themselves as AC experts. A lot of this stuff is full of errors and corner-cutting that would be damaging to a car that someone might really want to keep, rather than just get it off their car-lot.

Here is some fairly recent Mobile Air Conditioning Society survey data about the AC service industry:

• 57% had R-12 and R-134a mixed together (up 10% over last year).
• 20% had R-22 in R-12 systems.
• 20% had two or more refrigerants mixed together (down 10% over last year).
• 30% contained hydrocarbons (propane or other flammable hydrocarbons).
• 2% had too much air.

The same survey also revealed that only one out of 10 technicians knew about EPA SNAP rules, the Significant New Alternatives Policy regulations that prohibit refrigerant venting, require recovery and recycling, prohibit the intermixing of different refrigerants or the use of flammable refrigerants.

Two out of five technicians also did not know the service fittings on an A/C system MUST be changed if the system is converted from R-12 to R-134a or anything else. And three out of five technicians did not know mixing R-12 and R-134a could cause problems.


Now Larry, that does not sound like you. But, the point is, neither should NCRS members be left to depend on other so-called AC experts. That is why I put this conversion list together and presented it to be critiqued by NCRS members, the most critical bunch of folks I know. (So far, my expectations are being met.) And your contributions have been greatly appreciated. If a picky NCRS member wants to do this conversion themselves, or have it done, I strongly recommend they be armed with a specific list of high expectations.

[Larry M.]

Re: To Change-Out AC Refrigerant, or Not?

Elliot:

There are a few published procedures for the R12 to R134a conversion that are good and complete. GM did one themselves many years ago. The EPA did another.

I can scan and send you one or both if you really want them. Or I could discuss this conversion with you on the phone and save typing. Let me know if you want this information.

I have helped many from California to Connecticut with their old Corvette AC issues, and so far haven't screwed it up.

Larry

[Joe L.]

Re: To Change-Out AC Refrigerant, or Not?

I still do not understand why someone would even contemplate a conversion of a car using R-12 refrigerant to R-134a. I could understand it when folks had the notion that R-12 was going to disappear from the earth. That has proven to be a greatly exaggerated notion and has totally failed to materialize. As I mentioned previously, the number of cars on the road utilizing R-12 has got to be extremely small and rapidly diminishing. With the exception of collector cars also equipped with air conditioning (that being a very small percentage of the collector car universe), of those that remain, the vast majority are probably "junkers" that aren't even worth the cost of A/C servicing. So, there are probably more cars CONTRIBUTING to the supply of R-12 through mandated recovery and re-use than there are cars needing R-12.

So, once again, why convert a R-12 collector car to 134a?

[Dick W.]

Re: To Change-Out AC Refrigerant, or Not?

I still do not understand why someone would even contemplate a conversion of a car using R-12 refrigerant to R-134a. I could understand it when folks had the notion that R-12 was going to disappear from the earth. That has proven to be a greatly exaggerated notion and has totally failed to materialize. As I mentioned previously, the number of cars on the road utilizing R-12 has got to be extremely small and rapidly diminishing. With the exception of collector cars also equipped with air conditioning (that being a very small percentage of the collector car universe), of those that remain, the vast majority are probably "junkers" that aren't even worth the cost of A/C servicing. So, there are probably more cars CONTRIBUTING to the supply of R-12 through mandated recovery and re-use than there are cars needing R-12.

So, once again, why convert a R-12 collector car to 134a?

When the changeover from R-12 to R-134a it was recommended to change out a R-12 system ONLY when you had a catastrophic system failure, i.e. compressor, evap, etc. There has never been an industry suggestion to just arbitrarily change over.