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R-409A substitute R-12 ?

Dale7905 on Thu May 07, 2009 8:58 AM User is offline

Year: 1991
Make: Lincoln
Model: Topwncar
Engine Size: 4.6L
Refrigerant Type: R-12

Hello All,

I've read some advertisements that R--409A can be used as a substitute for R-12. I'd like to get some comments on whether it is advisable to use R-409A in auto a/c systems that use R-12 ?

It appears the cost of R-409A is about half the cost of R-12. After repairing my Lincoln's a/c I still have a few 12 oz. cans of R-12 left, but I'm still in the process of checking the system out. If the system has any leaks I will probably have to use all my reserve R-12 up and wonder if the R-409A might be an acceptable refrigerant to add to the R-12.

Any comments or recommendations would be greatly appreciated.


TRB on Thu May 07, 2009 10:23 AM User is offlineView users profile

Autofrost has been discussed a many times already. Do they still even manufacture this product? Website is dead so I can only assume the product is not being backed much anymore!

Previous Autofrost discussions.


When considering your next auto A/C purchase, please consider the site that supports you:

mk378 on Thu May 07, 2009 5:30 PM User is offline

Mixing refrigerants is very bad practice as well as illegal. You would use either pure R-12, or pure substitute with no R-12.

After closing up the system, do a static pressure test before evacuating and charging with R-12. You can use R-134a and/or nitrogen for the test. This is just where you fill the system with some gas and see if any leaks out. Since it's your car, you have the luxury of waiting a couple of days to be really sure. Do not run the compressor.

Peter_Coll on Fri May 08, 2009 10:38 AM User is offlineView users profile

R409a is composed of 60% R22, 25% R124 and 10% R142b. The seals in your vehicle may not be tolerant of the R22. In addition, R22 and R142b are on the way to being banned and the price of R409a is likely to go up significantly.

To be are working on a system that would cost a few thousand dollars to replace and worrying about saving 50 bucks on refrigerant seems a little TOO frugal.

Dale7905 on Fri May 08, 2009 8:56 PM User is offline

Thanks for all the comments. They were very informative and helpful. In re-reading my original post I felt I could have been more clear in explaining what I had done so far. Actually, I had replaced the compressor, condensor, accumulator/dryer, and 'o' rings over the past couple of months. The compressor was the latest repair. I then pulled a vacuum to about 250 microns. The vacuum after about 12 hours climbed to about 300 microns. This I took as an indication that the system was pretty well sealed and with a bit of luck would not have any major leaks when charged and operating. I'd recharged the system and checked the pressures with the a/c running and measured the temperatures from the dash vents. Since Tuesday ( 5 May) the a/c has been working well giving me vent temps down to 40 degrees F . But I'm a believer in 'hoping for the best, but preparing ( or trying to prepare ) for the worst'. That resulted in my trying to locate some sources of R-12 in case the a/c did develop a slow leak and I'd have to use up my remaining small amount of R-12.

As I browsed the Internet for R-12 sources, I came across the R-409A refrigerant and notes that it was a replacement/substitue for R-12. That prompted my post to this forum. As usual I learned a lot from all the responses. Fortunately, my problem of finding some R-12 at a reasonable price ( for me at least) has been resolved. A friend I talked to about trying to find R-12 knew someone who had some he was trying to get rid of. As a result, I was able to get enough spare 12 oz. cans to allow me to forget about the R-409A option. Interestingly however, I found an alternative souece on Craigslist. A fellow had a 30 lb can for $350 in the Baltimore Md. area. If anyone is looking for R-12, that's a great buy in todays market I would think,

Thanks again for all the comments. This is a great forum.

Chick on Fri May 08, 2009 9:31 PM User is offlineView users profile

R409A is a great replacement for R12 in "stationary" refrigeration applications, where hard lines contain the "blend".. . Not in automotive applications due to the amount of R22, and being a blend is not a good idea either, they fractionate when they leak out, one blend leaks faster than the other and leads to catastrophic compressor failures.. Stick with the "Two" automotive refrigerants, R12 and R134a.. Just my opinion..

Email: Chick


Freedoms just another word for nothing left to lose

Dougflas on Sun May 10, 2009 11:28 AM User is offline

R22 when used with rubber hoses will let the refrigerant penetrate thru the hoses.

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