Automotive Air Conditioning Conversion: R-12 to R134a

  From: Chris Hawkins  (July 2007)

Whoever told you the condensor needs to be changed should be looked at with suspicion. They would appear to be unfamiliar with the overbuilt, high capacity nature of the AC system on a '66.An R-134 retrofit should be a straightforward procedure.

For best performance, the only alteration to consider is to remove the EPR valve from the back of the compressor and install an adjustable thermal compressor clutch cut-off switch. That is because R-134 will easily take the evaporator temp down below freezing and the thermal switch can be adjusted to keep airflow around 34 degrees. The stock EPR valve is not completely happy with R-134 and might not provide cold enough air if you live in a very hot climate. That is the component that restricts flow, not the condensor.  

Original question:

For 66 imperial ac retrofit, I was told that the condensor needed to be changed for a high flow model, of course the receiver/dryer needed to be changed, a flush wouldn't hurt. The oil needs to be changed fromthe original mineral oil to ester (ester works with both R-12and R-134a, PAG only with R-134a).Doesanyone have experience with a retro fit where the condensor was not changed and the
AC worked well? I really don't want to change the condensor and would be forced to recharge with R-12 after replacing the V2compressor which failed (from Advance Autoparts, or some other source if someone has a good place in the San Fernando valley. Thanks. 

Original Tech

What does the factory say?I got this from a Chrysler dealer employee in August, 2001:

"Regarding converting to R134a - Chrysler came out with a bulletin, including part numbers on most mid-'80s and up vehicles. I think that they went a little overboard, probably just trying to protect themselves from lawsuits down the road. In reality, the only part that needs to be replaced is the receiver/drier, not with anything different, just a new one. The system needs a real good flush to get all of the old R-12 out, and also replace the refrigerant oil with 'ester' oil, I believe. In addition, the screw-on adapters for the Schraeder valves need to be added."

The following is a June 1999 exchange of email messages on the IML on experiences with converting from R-12 (CFC-12) to the most popular, currently-produced automotive refrigerant, R134a (HFC-134a).You should also read what the EPA says about this conversion at:

I think all the following messages are consistent with the EPA advice and provide very valuable different points of view.

A/C Retrofit to R134a -- What Do I Need to Know?

Fallacy Corner

by Joe Stefanick

(This is an article that I wrote for one of the many car clubs that I belong to. Some of you have seen it already. It doesn't hurt to pass along good information.)

About a year ago, I wanted to get the A/C fixed on my 1974 Imperial LeBaron, and started researching the costs and what was involved. After much research and conversation, I came to the conclusion that the A/C fix could be costly, as the cost of materials (R-12 or CFC-12 in particular) is very expensive. At any rate, right smack dab in the middle of the A/C fix research process, and totally unrelated, I ended up buying a real nice, relatively low mileage 1976 Chrysler New Yorker. I put the 1974 LeBaron's A/C fix on hold, as I now wanted to concentrate on the New Yorker, again whose A/C was not functioning. After more research, I came to the conclusion that only solution to my non functioning A/C was to convert the system to the newer R134a (HFC-134a) gas.

The Driving Force to Convert to R134a

The main reason for going to the conversion was the prohibitive cost of the R12. On a good day R12 costs start at about $30 per pound. With this large New Yorker requiring about 3 pounds of A/C gas, we are talking about an expensive proposition using R12. Especially if after the system is recharged (which can happen when the system is re-pressurized) the gas escapes and you have to refill the system again. Wow! $90 for gas times two. Knowing this bit of gas cost information, and knowing that R134a costs about $6 per pound, made the decision to convert very easy.

The Fallacy

I am sure all of you have heard when you convert from R12 to R134a that you must swap out the compressor, all the system "O" rings, the receiver/dryer, etc.. Oh, my God, the whole system needs to be replaced!? Well guess again.

What is Necessary for the Conversion

Actually, very little is required, as long as your compressor, expansion valve, dryer, condenser, and evaporator are sound. A good auto technician will be able to check the functioning of the components mentioned and replace those that are malfunctioning (see my previous article and what to look for in a good auto technician).We are assuming that the system was functioning before the R12 escaped.

What needs to be done

  • Find gas leak in the A/C system and repair
  • 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
  • Completely evacuate the system
  • Install new gas input and output stems. This prevents R12 being mixed with the R134a gas in the future
  • 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
  • Place a retrofit sticker on the A/C system stating it was converted to R134a usage

An Idea of the Cost Involved to Convert my 1976 Chrysler New Yorker

My system needed a number of things as it had been sitting for quite some time:

Compressor and Clutch




Expansion Valve


Conversion Kit (oil & new system valve stems)


EPR Valve


Retrofit Conversion Labor




I recently had a conversation with a close friend of mine who has considered getting the A/C repaired on his fine antique automobile, and was quoted $1,300 for a conversion from R12 to R134a. I am not sure what they were doing for the conversion, but even if you factor in market price for the parts, the cost will be at most about $1,000. I didn't get a chance to find out exactly what was being done for $1,300. BUT it sounds like the fittings are to be gold plated, or more likely the repair shops pockets are to be gold lined. A word of warning - find out exactly what is to be done when your system is converted (i.e. the actual conversion process and what non-functioning components are to be replaced).

An Experience You Won't Forget

If you are ever in the Philadelphia area, and want to experience how cold the converted system in my New Yorker gets, give me a call and I'll give you a ride. I had my New Yorker out for our LCCI Invitational in New Hope this past May. On the drive to the meet, the ambient temperature was about 90 degrees Fahrenheit. The New Yorker's R134a A/C system put out about 42 degrees at the A/C registers -- it was very comfortable in my New Yorker on that hot day.

For further information or questions, please feel free to call me at phone 215-643-9229.

Comments by Ron (

It must be that time of year again, I swore I was going to stay out of this but those darn hairs on the back of my neck!

I would like to understand where you came up with $200 for labor. For that retrofit labor, I have a lot of sub work I could send to that shop! I added up the non overlapping FLAT RATE hours for the above work and without any time allowed toward diagnostics, or evacuation and recharge the FLAT RATE HOURS comes to 4.8 Hours, that means your model shop has a FLAT HOURLY RATE of $41.67/hour, where in this country is there such a low overhead shop with competent techs? When I add in the usual 1 hour diagnostics, and another 1/2 hr (optimistic) to dial in a "never before had R134a system", that comes to 6.3 Hours which equals a shop charging $37.75/Hour.

I know - what's my point?

SOME OF MY points are:

  1. NO TWO SYSTEMS ARE THE SAME, or have the same problem, or will convert exactly the same, or will COST the same --- period.
  4. MOST SHOPS LIKE TO PAY THEIR BILLS and their EMPLOYEES like to take home a LIVABLE PAY CHECK, and around here that means A FLAT RATE of about $65/hour for a non-dealer shop. I haven't found a way to "gold plate" my pockets doing A/C conversions, the truth is that most "classic cars" we CONVERT are among our LEAST PROFITABLE
  5. BLANKET STATEMENTS and inaccurate examples only add to the confusion, and after 5 years of conversions, I still get an education on most systems that I do.

Soap box idling Ron

Comments from Dick Benjamin

Just to support Ron's statement (and trying NOT to add any fuel to the discussion), but after 50 years of working on old cars, doing it as my own profit-making (Hah!) business for a 15 year part of that time, I can honestly say that nearly every car presented something I had not seen before, and consequently taught me something new and worthwhile. Regardless of the shop labor rate, I always wound up donating much of my time at no cost to the customer sorting out the weird problems we got presented with.

I learned the hard way never to make a blanket statement about what something was going to cost or take in the way of parts or time.

One way to run a business doing that is to overestimate the potential cost (which scares away some customers) and then overcharge the ones that bite to make up for the really bad baths you inevitably take. This is the well known national chain's approach to transmission repair. Not an example one wants to follow.

Further comments from Joe:

Hi Ron,

The price of $200 comes from Jack Crowley at C&J in Berwyn, Pennsylvania -- a suburb of Philadelphia. Jack operates on volume and keeps his pricing accordingly low. What I would recommend is to give him a call at 610-647-6072.

Jack is a nice guy, and will take the time to explain his pricing structure.

To date Jack has performed over 300 conversions - his Mercedes being the first to get the conversion.

I have sent one of the guys in my LCCI club to have his Bimmer converted - the cost to Tom was $200.

Please let me know if you have any more questions. As a matter of fact, if you have questions not answered by the article, or have further questions, please give Jack a call yourself and assuage your curiosity. You obviously live in a different part of the country than he does and he won't be able to profit from you. Jack will give you and honest appraisal of what is involved in a R134a conversion.

Joe :-)

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