How often does AC need to be recharged?

I advise you to do it whenever it is obvious that it needs to be recharged. I once lived in Virginia and did not use the AC during the cold winter months. I had to have the AC recharged at the end of winter since my AC no longer produced cold air. Some of the auto related stores such as NAPA have special thermometers that clip on to the AC vent. Jason

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Just changing the cabin filters will make a huge difference. I do them at least yearly. But if it's not that, I can't say.

'Curly'

With the older R-12 systems, it was recommended to run the AC at least once every week for about 10 minutes throughout the year just to keep the seals lubricated and protect them from drying out. I don't know if this recommendation still holds true for the R-134a systems.

Eric

It theoretically should never need to be recharged. In practice, systems start leaking eventually and do need a recharge, but a 2001 is a little new for that. I figure at the ten year mark about half of A/C systems have needed recharge.

If your A/C is getting weak, you can change the cabin filter as Curly recommends. If it has been changed recently it's time to schedule a checkup with an A/C professional. In the R-12 days you could do almost everything yourself, but R-134a is a very diffferent beast. I don't know why, but I had no trouble recharging R-12 systems and failed miserably the time I tried to recharge an R-134a system. Worse, regulations have made the overhead very high for professionals. That means you can expect to part with most of $100 US for a check-up, which involves emptying the system by filtering and capturing the refrigerant then refilling with the measured amount of R-134a. A check of the operation, along with fixing or identifying air flow and control problems completes the job.

To rub salt in the wound, a decade after the ratification of the Montreal Protocol - which included banning the production and mandating other controls for R-12 and other CFCs - A NASA/NOAA mission called POLARIS determined CFCs (in fact, all halogens combined) have only a minor effect on stratospheric ozone depletion. The main culprit is reactive nitrogen oxides, formed by sunlight. Isn't that special?

Mike

but it was a great business opportunity! from what i understand, r-12 was out of patent, made by many companies and competitively priced. r-134a otoh...

I have a 94 Accord, which I think was the first year of

134a. It isn't so cool now, and cycles frequently. I was planning to get a can of 134a at Wal-Mart, and the connector/hose, and just charge that into the low side like I used to do with R12 systems. Are you saying that doesn't work? If so, I sure would like to find out why.

If you're saying they have to evacuate all the old refrigerant, and add back the correct amount, rather than just adding more in the first place, I wonder if this is "regulations" or just the standard repair scam bullshit.

I sure would like to get an explanation, in scientific terms, of why you can't just add a little 134a. Do pressure gauges not work with 134a? Do they not tell you whether the charge is correct?

I don't know why it is so, but even with plenty of experience with R-12 and a guage and thermometer I was unable to find the correct charge for my son's Acura. It turned out the correct charge was about half the bottle. When we were done I could hear liquid drops hitting the compressor so I told him to leave it off until he got it done right. I didn't want to ruin his compressor.

We added gas slowly and I watched the pressure and vent temperature, but it never was anywhere near correct until it was done by weight. I can only guess the lag time in the system is very long compared to the half minute or so it takes R-12 to stabilize. A friend who went into refrigeration before he moved away told me that with R-134a the condensor pressure is more critical than it is with R-12... that may be why it can't be done by ear any more. If the condensor has to stabilize to evaluate the state of charge it could take hours to do it "by ear." But that's only a guess to explain my failure.

Mike

[snip]

A can of R-134a contains both refrigerant and lubricating oil, and I have read that the practice of charging without purging can, over time, result in significant accumulations of excess oil, giving rise to unusually high operating pressure and leading to premature seal failure.

Thanks. But I still think we need to find an authoritative technical explanation.

Please let us know what you find. It's always good to know these things.

Mike

$920 later I just found this out. I had a small leak that only happened when the unit wasnt used for a week or more. I added oil and a recharge can of

134a and my compressor locked up a month later. Was real cold for a month though! Mechanic told me the same thing, too much oil and shouldnt be done by shadetree mechanics wiythout meters.

Ow! That lesson was a dear one! I do know that overcharging any A/C sysem will cause liquid to overflow the evaporator and "slug" the compressor. Very bad news.

Mike