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R-12a Refrigerant For A/c

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I had a POA valve (back pressure control valve on a/c system) go out on me and the

a/c repair shop wanted about $800 to correct the problem. Around $400for a new

OEM valve replacement, over $100 to replace 36 oz of R12 refrig ('93 SC400 had this refrig)

and the rest in labor.

I said BS and decided to tackle the job myself. I found a OEM replacement valve,

brand new, for $145. It was a bit of a struggle to get the new valve in but I managed without

a lift rack which would have helped a lot.

Now, the replacement refrigerant. I did not want to convert my system to R-134a because

of its poor cooling efficiency so I elected to go with R-12a (bear with me before you call me

a complete idiot).

After pulling an almost perfect vacuum on the system I first added 4oz of ester oil from a

can precharged with R-12a followed by the additon of another 10oz of R-12a for a total

charge of 12oz of refrigerant as opposed to the 36 recommended charge of R-12... probably

about $150 even if I could get it as an unlicensed user). So, my total cost for the job was

about $185 bucks including the rental charge for a vacuum pump. R-12a runs about $7/6oz


On checking out the system on the road, the temp exiting the center air vent was 48 degs F

and the cabin was as cold as I have ever experienced in just a short period of time. This

stuff has awsome cooling properties and you can hardly tell the compressor is on.

Before I plowed into the venture I researched the s--t out of R-12a on the net. I have a a BS

in Chem Engr so it's not like I am oblivious to understanding physical and chemical properties

of materials. In summary, the findings reveal that basically the whole world is using the

equivalent to R-12a in all the refrigeration uses such as cars, refrigerators, commercial buildings,

chemical processes, ect. The net savings in energy costs are has much more

cooling efficientcy due to its molecular structure and requires significantly less horsepower

during the compression cycle. The refrigerant is fundamentally methane and yes, it is more

flammable than R-12 and R-134a because it does not contain a halide( chlorine or fluorine).

Its auto ignition temp is much higher than 134 and it is totally environmentally safe and thus

goes by the trade name ES -12a. Because of the flammablity properties the US has not sanctioned

its use here yet but just like our strict drug policy it will change with time. There are no legal

restrictions with regard to purchasing and using the product.

Rather than me trying to cover all the ramifications of the product/safety issue, I have listed two web

addresses below if anyone is interested in learning more. It's corrosive properties are nil and thus a

complete changeover from std 12 or 134a would be very easy..all explained in second site below. --- safety issues discussed and specification information

PS-- If this topic has been discussed before forgive me for the long winded post.

I could not find any past discussion except maybe one referring to Freeze 12.

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With a proper charge of the factory original R12, the AC outlet temp is in the 35-42 degrees range so your system is not very cool now if it is putting out only 48 degree air.

36 ounces of R12 costs only around $40 on ebay ($30 in the winter months) and anyone can get certified to buy it if they merely pass a 25 question multiple choice open book $15 exam at

Your system was designed to run on R12 and a factory specified Suniso or Denso compressor oil. Putting other refrigerants and oils into it will severely degrade system reliability and durability. There are a dozen or more "R12 substitutes" out there on the market and some cool as well or better than R12 but none provide the long term system reliability and durability of R12 and the factory original compressor oil

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Cooling air outlet temperature is a function of inlet temperature, blower speed, and refrigerant/system cooling efficiency.

48F might have been stellar performance for all you know.

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Blower fan was at max and I was only a few minutes into the checkout

and felt satisfied because the cabin temp was very cool. Outside temp

was around 90 so car was hot..typical Florida.

R12 may be the refrig of choice but it apparently resulted in deterioration of the rubber diaphram in the POA valve and caused my problem to begin with. I also replaced two 'O' rings which were suspect.

The corrosivity of R-12a is nil compare to halogen containing refrigs

which just are not friendly to rubber components such as 'O' rings,

diaphrams and gaskets over the long haul.

Can't really comment about ester oils vs the mentioned Suniso/Denso

oils but the vendors claim total compatability of their precharged oil

cans with both mineral and synthetics. Of course they are selling the

product so maybe that is what you would expect them to say.

Compressor runs the same on the low side but about 15psi less on the high side which equates to around 3hp less load. Not sure what this

does for gas milage but I wouldn't be supprised if an improvement of

1 mi/gal might not result.

May be sorry down the way but so far satisfied with the change.

Thx for your comments.

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R12 may be the refrig of choice but it apparently resulted in deterioration of the rubber diaphram in the POA valve and caused my problem to begin with. I also replaced two 'O' rings which were suspect.

For decades and decades AC engineers have been preaching that the key to keeping an auto AC system troublefree is run the system at least once every week or two throughout the year, including in the winter. The keeps all the rubber parts and seals in the system pliable and lubricated and prevents wear and corrosion of the metal parts. I have a 13 year old Toyota with 436,000 miles with no AC system troubles at all despite heavy use since I live in a hot climate. I just make sure to run the system for a few minutes once a week during the cool winter months.

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monarch-- amen to lack of use. I am the original owner of a 1965. 289 Mustang with only 98K actual miles and have had to replace the rear

transmission seal 3 times because of lack of driving.

In the SC400's case, it is driven several times weekly and I guess I just had bad luck with the valve. I still like the route of going to a non-halogen refrig and if you go into depth on this subject, billions of $

in energy costs could be saved in the US if the standards were reduced.

A lot of hanging on to the refrigs we use here is highly political.

Enuf of this subject, lets go on to things that are more important to the

other forum members.

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