QuestionQUESTION: Thanks for considering this. 95 Suburban, think I found where my refrigerant leaks out: its where you put new refrigerant in - after I added a can and removed the pop-on fitting, I could see some bubbling out of the nozzle. Can I clean this so it won't leak, or can it be replaced?
ANSWER: These fittings are normally capped with an O-ring equipped cap which seals the valve when it is put back on after servicing. Techs who are not familiar with servicing R134a systems may discard the caps, thinking that, as on R12 systems, they are just there to keep out the dust and dirt. But, R134a is much better at leaking out through microscopic gaps, which is why they use a different type of hose and different materials in the O-rings and seals. So, if this cap is missing, you need to get a new one and make sure you put it on tightly. Second, get a new valve core for the fitting, the old one may have perished from age. Any good-sized auto parts store should have these things in stock, just make sure you tell them the make, year, and model, and that it's for the low side fitting. You might want to get a pro to put this valve in; he will have the tool needed to unscrew it and screw in the new one, and he can salvage the R134a that is left in your system. Get him to vacuum out the system while he's doing it, he sort of has to anyway. Then, you should be good to go. Modern A/C systems look and act a lot like the old R12 systems, but they are a lot more finicky about doing things absolutely the right way; it's almost always a good idea to pay the extra cash for a professional job.
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QUESTION: Mike, great thorough answer, thank you. Question: since my R134a has probably leaked out, is that valve something a shade tree could change out? What kind of speacialty tool is needed? I have various spreader-type pliers if that would work.
ANSWER: You could certainly change it yourself if all of the refrigerant is gone, although you're going to have to vacuum down the system before installing the new R134a. The new charge should be weighed on a refrigerant scale to make sure you don't over- or under-charge the system. The tool you need looks just like a tire valve stem tool, but is probably a different size. I'm sure you could buy the tool pretty cheaply, or modify a tire stem tool to work in its' place for even less.
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QUESTION: That probably makes me unable to do that part of the repair, because I suppose there is no easy way to vacuum the system. What if the leak is only due to the lack of the O-ring equipped cap you describe? Could I add a couple cans and put on the new cap? I'm about to hit the sack, but I'm sure grateful for your sharing your know-how, and getting back so promptly.
Answer You could do that, and it would work for, probably, quite a while. The problem is that when refrigerant leaks out something has to replace it, and that something is air. Air is made up of mostly Nitrogen and Oxygen, and Oxygen is a highly reactive substance (see, for instance, fire). R134a is also a reactive substance, and the oil circulating in the system is even more so. One of the results of these reactions is acids, which can then eat away at the components of the system. Believe it or not, the damage caused directly by the acid isn't the problem, but the byproducts circulate in the system and clog up the orifice tube and the small passages in the evaporator core. So, you can get away with what you want to do, I think, and maybe the truck is old and worn out and doesn't deserve a lot of money spent on it, but I would still honestly recommend doing it properly. It could get real hot this summer.
