hello all, i have a depleted A/C system, but it still has head pressure. The sytem has never been opened, and was removed (whole system) from my donor 1989 iroc and transplanted.
Point is, I can get cans of R-12 cheap (6-7bucks) here in Japan. I can have the local gas station recharge the system for 30 bucks american. I have heard that "OLD" systems are prone to leaking and should just buy all new stuff, ie; compressor, dryer, condensor, all new seals...
Should I go ahead and try to refill the system, or let the gas station do it? I would rather stay r-12, than have to PURGE the system, then add R-134.
whatcha think?
shawn

 

Get the system evacuated. See if it holds vacuum, if it does, your set, if it leaks, find the leak and replace the part. For 30 bucks, if you fill it and it lasts a few months or so, its prolly worth it. You cant get r12 that cheap in the states anymore. As for converting it, some may say yes some will say no.... I think most will lean towards no. In my opinion, the new stuff sucks, and doesnt get as cold as 12. I would assume with properly matched components designed for the new stuff, it could get pretty cold. I would get it sucked down and throw the right amount of 12 in it and see how long it lasts.

 

Correct. And if the system leaks with R-12, it will certainly leak with the R-134 running at higher pressures to provide less cooling. R-12 doesn't cause any leakage any more than any other type of small system refrigerant. The systems get old, have problems, and leak. Repair the leaks, install a good filter/dryer, evacuate as instructed, and add the correct refrigerant and compatible oil charge. If you can get R-12 that cheaply, go for it. Just be careful you don't have trouble importing it. It is now a controlled commodity in the U.S.

 

R 134 stands for the molecule size...it`s very small, R12 is a large molecule...it will take longer to leak out because of it`s size. (not because of high pressure) I have done hundreds of conversions to 134a from r12 and the newer refrigerent runs at roughly the same pressure as r-12, in fact if you have an adjustable low side cut out, 134 runs best at 20 psi low side and 150 psi high side at 75*. If it`s converted you`ll need to replace the reciver drier that has the desecant bag..it holds the dino oil that the 134 is not compatible with. Pag or estercool oil is the only thing to use on a conversion. The seals are also a must the new oil/ref will attack the rubber seals over time. Stick with the twelve it does cool faster and gets colder period.

 

well, I found an A/C vacuum puller in my harbor frieght catalog. Says to just "hook up 90 psi and 4.2CFM and it will pull a 28 inch vacuum in 2 mins." It is 14 bucks so that is not bad. I can check system for leak down. then take it to the gas station for the fill up. Sound like a plan? I can't drive the car yet as it has no plates, so i am prone to trying most fixes here in the carport. Much thanks again. shawn

 

A correction

R-134a is 1,1,1,2-tetrafluoroethane

R-12 is dichloro-difluoro-methane



The molecule on the left is R-134a -- The molecule on the right is R-12

With R-134a, there is a 2 carbon chain with 3 fluorine atoms on one of the carbons, and 1 fluorine and 2 hydrogen atoms on the other carbon. R-12 has only one carbon with 2 fluorine and 2 chlorine atoms attached.

The number in the R-xx is not molecular size, it is just a numbering convention.

from http://www.epa.gov/ozone/snap/refrig...ackground.html

 

thats cool, but what do you think of the game plan?

 

If the system is still holding some pressure, it should be in decent shape and air/moisture free. Considering the price, I'd shoot the R12 in it and go cruising.

 

thats not necessarily true. he said it had head pressure. if it has been run with a leak, the suction side could and probably is in a vacuum meaning the system is not that clean. if I were king, I would pressurize the system with nitrogen, find and fix your leak, replace your drier, and recharge it with 12 if you can get it that cheap.

 

Throw in a couple of cans of R-12 and see what happens. If it leaks, you are out $12. And add a can of the UV dye so leaks can be detected.

 

Better re-check your T/P charts. While the evaporation point vapor pressure is slightly lower at lower temperatures, it rises sharply when temperature increases. By the time you REALLY need cooling (at 95°F ambient and above) condensing pressure is just stupid-high at over 20% higher than the R-12, and all while moving considerably fewer BTUs per mole of refrigerant gas. The older system designed for R-12 just isn't suited nor designed for the pressures exhibited by R-134 during cooling.

Incidentally, numeric designation is not necessarily related to molecule size: http://www.epatest.com/q_ref_numbering_system.html

 

Nice info on the post, but a few of the molecular formulas are jacked up. R-12 has 2 Cl, not 3. Saw a few other blunders.