rangerj
Active Member
Gentlemen, and ladies,
I have done dozens of conversions of R-12 to R134a in a variety of makes and model vehicles (including my 90 SHO). I have had no problem getting 35F to 38F degree temperatures out of the center vent of the dash of any of them with R-134a.
A few years a go I had two identicle vehicles on the same weekend that needed new condenser cores. One was recharged with R-12, and the other was converted with R-134a. Both got new filter dryers and the evaporator cores were flushed with the same chemicals. Both compressors were drained, overnight of their oil, and got fresh oil.
After being assembled with new connection gaskets, both systems were vacuumed the same amount of time to remove any moisture (water). One was charged with R-12 ($65 lb.), the other with R-134a ($10 lb). The R-12 vehicle owner made some of the same claims of cooling efficiency made in these threads.
As a test, both cars were started and brought up to full operating temperature and then put on max A/C. An A/C thermometer was placed in the center vent in the dash of each vehicle. They both reached the agreed upon test temperature of 40 degrees F within seconds of each other.
Both R-12 and R-134a have boiling points at temperatures below 150 degrees below zero. A liquid boils by absorbing heat, that is the premise of an A/C system.
If we were to take two equal containers of refrigerant, one R-12 and the other R-134a, and open them at exactly the same time at room temperature, I would defy anyone to tell which evaporated (boiled) first using any, or all, of your five senses (sight, hearing, touch, taste, smell).
The one that evaporated first would be the "most efficient" at absorbing heat, right?
It has been my experience that the reason folks are not happy with an R-134a conversion is because it was not done properly. An old worn down compressor will not work any better with R-12 than it will with R-134a.
People want to make the conversion, but do not want to pay for a new compressor. Then they gripe because the R-134a isn't "efficient".
The difference in efficiency is not because of the refrigerant. The difference in efficiency cannot be percieved by the five human senses. By the time a system gets converted it is already old and worn.
Folks want the A/C to work, but the car is usually old, and they do not want to spend the money to properly repair the system to maximize the efficiency of the refrigerant.
As for the "compatible" additives or substitutes for R-12, they contain a significant amount of methane or butane and are EXPLOSIVE. Most "pro" shops will not touch the stuff.
Anyone interested in how to do a "proper" R-134a conversion, there is a complete disertation on the subject in the threads from last summer. Or just ask, and the forum members, including myself, will offer our opinions and experiences.
Lastly, if you want to know more about the theary and the physics of air conditioning, stop by a university book store and pick up a book on "thermodynamics" (found in the Engineering section). It's cool stuff (get it, "cool"). thumbs_u thumbs_u rangerj
I have done dozens of conversions of R-12 to R134a in a variety of makes and model vehicles (including my 90 SHO). I have had no problem getting 35F to 38F degree temperatures out of the center vent of the dash of any of them with R-134a.
A few years a go I had two identicle vehicles on the same weekend that needed new condenser cores. One was recharged with R-12, and the other was converted with R-134a. Both got new filter dryers and the evaporator cores were flushed with the same chemicals. Both compressors were drained, overnight of their oil, and got fresh oil.
After being assembled with new connection gaskets, both systems were vacuumed the same amount of time to remove any moisture (water). One was charged with R-12 ($65 lb.), the other with R-134a ($10 lb). The R-12 vehicle owner made some of the same claims of cooling efficiency made in these threads.
As a test, both cars were started and brought up to full operating temperature and then put on max A/C. An A/C thermometer was placed in the center vent in the dash of each vehicle. They both reached the agreed upon test temperature of 40 degrees F within seconds of each other.
Both R-12 and R-134a have boiling points at temperatures below 150 degrees below zero. A liquid boils by absorbing heat, that is the premise of an A/C system.
If we were to take two equal containers of refrigerant, one R-12 and the other R-134a, and open them at exactly the same time at room temperature, I would defy anyone to tell which evaporated (boiled) first using any, or all, of your five senses (sight, hearing, touch, taste, smell).
The one that evaporated first would be the "most efficient" at absorbing heat, right?
It has been my experience that the reason folks are not happy with an R-134a conversion is because it was not done properly. An old worn down compressor will not work any better with R-12 than it will with R-134a.
People want to make the conversion, but do not want to pay for a new compressor. Then they gripe because the R-134a isn't "efficient".
The difference in efficiency is not because of the refrigerant. The difference in efficiency cannot be percieved by the five human senses. By the time a system gets converted it is already old and worn.
Folks want the A/C to work, but the car is usually old, and they do not want to spend the money to properly repair the system to maximize the efficiency of the refrigerant.
As for the "compatible" additives or substitutes for R-12, they contain a significant amount of methane or butane and are EXPLOSIVE. Most "pro" shops will not touch the stuff.
Anyone interested in how to do a "proper" R-134a conversion, there is a complete disertation on the subject in the threads from last summer. Or just ask, and the forum members, including myself, will offer our opinions and experiences.
Lastly, if you want to know more about the theary and the physics of air conditioning, stop by a university book store and pick up a book on "thermodynamics" (found in the Engineering section). It's cool stuff (get it, "cool"). thumbs_u thumbs_u rangerj
