Air conditioning in the older R12 cars

R12 is dichlorodifluoroethane. It is a molecule with one carbon atom, two chlorine atoms and two fluorine atoms. It's bigger than a water molecule. If it won't leak through things the way hydrogen gas leaks out (or for that matter, hydrogen sulfide, which tends to leak out of kids at the worst times and stink up the room).

R134a, which is usually used to replace R12 is 1,1,1,2-tetrafluroethane, a n even larger molecule with two carbon atoms, two hydrogens and four fluorine atoms.

I would suggest taking it to another mechanic. Sometimes, taking a problem to a new person does the trick when the new person looks at it with new eyes.

Jeff

Your problem isn't R134a but bad mechanics. My former neighbor restores cars and converted a couple of his 1960s cars to R134a and installed an R134a system in his Karmen Ghia but never had A/C problems with any them. Also my 1998 Nissan with R134a and 1986 Toyota with R12 have leaked a lot less than my 1993 Ford with R12, despite the latter having a lot fewer miles, probably because Ford used crappy press-in spring lock couplings instead of conventional ones.

R134a leaks worse than R12 and requires better seals, so factory R134a systems are made with hoses lined with nylon to prevent R134a from diffusing throughthem. OTOH _used_ unlined hoses in R12 systems are fine because all the oil they've absorbed over the years also blocks diffusion. Also if any hoses were replaced in your car, was the new rubber crimped to the metal fittings, as virtually required for R134a, or were barb fittings with hose clamps used? And were the fittings and o-rings properly oiled before assembly?

Here's a FAQ about R134a conversions:

is a great site that specializes in automotive A/ C.

has back issues of Motor magazine available, back to

1998. They have an A/C issue about every other year (April. 1999 is one).

Barrier hoses help but non barrier should only require a charge every couple of years. If it is any faster than that there will be a leak that can be found using an electronic sniffer. What helps the most when converting to

134a is to replace the condenser with a parallel flow model.

Also R134a is not a Freon, Freon is CFC and HCFC refrigerants such as R12 and R22 made by DuPont chemicals. Other companies had other names such as Genetron for 12, 22, etc.. DuPont refers to R134a and all other HFC refrigerants they make as Suva.

You need to trade it in for an '02 Corolla.

SHE SAYS R134a leaks because the molecules are small.

YOU SAID R134a molecules are larger than R12 molecules.

Seems to me that maybe an air conditioning shop is in her future. Assuming you are right -- and I do not dispute that point -- then the leaking has to be from a fitting or other joint someplace. One thing that is true is that R134 dries the rubber that is used in R12 systems, so if all of the o-rings were not replaced when the system was changed over, then that is a very likely source of the seepage.

You gotta remember that "freon" is a generic term, like Kleenex. Both are product names, but we use the words in a generic sense. If you ask for a kleenex to blow your nose, you are not gonna be upset if you get a lowly tissue. Indeed, you would probably not even notice.

And, she did specify "newer kind of freon," so she knows it is different.

yes.

You are trying to make a silk purse out of a sow's ear. Retrofitting R12 systems with R134a has always been problematic at best. At absolute best, the cooling performance is degraded.

Suck it up.

But, the molecules of R134a are bigger than those of R12 (and both are larger than those in water).

I know, but to me it is kind of like asking for a Kleenex and getting a paper napkin instead. If you ask for Vise-Grips you will get locking pliers of some kind, ask for Channel locks and get adjustable slip joint pliers, Calling an HFC a Freon is like asking for a Crescent wrench and getting pliers.

The comparisons have their problems. Freon is a trademark used for a particular group of refrigerants. The numbers and sometimes letters of the R (like R-12 and R134a) specify the particular types of atoms in the compound. (Look up Freon in Wikipedia for the details).

Otherwise, it is hard to think of a better comparison that is so simple.

BTW, the name for this group of compounds is HCFCs (hydrochlorofluorocarbons - for the name of the elements in the compounds), not HFCs.

If you changed the compressor last fall, and have had multiple times where it ran low, that is not a small leak. That is fairly large, and should be fairly easy to find. The problem seems to be relying on a dye rather than using a detector. If you have a leak in the evap coil, the dye will be useless. He needs to be using a proper detector. And this is no small leak, so it shouldn't be that hard to find. Be aware that the rate of leakage will vary to which side of the system the leak is on, "high or low pressure side", and whether it's running or off. Fer instance, a leak in the evap coil will leak the fastest when the system is not running. A leak in the condenser coil, or other high side lines will leak fastest when the system is running. Believe it or not, I can usually hear a leak of most any decent size. I've done A/C work since the late 70's, and I've found as many leaks with my ears as I have with my detectors. I can hear them most of the time if it's quiet. Pssssssssssssssssssssssssssssss..

I already said that.

Per DuPont:

CFCs and HCFCs (R12, R22, etc.)=Freon

HFCs (R134a etc.)=Suva

Depends on the audience.

Contextually, you'll know if the person is asking for a "refrigerant that goes into my AC system" or is asking for a specific chemical.

If you can't figure that out, you have lots of problems in life.

no, I meant that "yes, people say that". Doesn't really mean anything.

I'd want to be careful with the names because some garages have sold what they called "Freon R-134" that were mixtures of R-22 and another Freon plus propane or butane.

That would be illegal, particularly because Freon is a trademark, this is false advertising and not providing appropriate service. Do these places also provide the transmission and wallet flush?

Better find a new mechanic. AC leaks are relatively easy to find with the proper equipment like a leak detector.