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Old AC Systems

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  • Old AC Systems

    Was reading on another forum about troubleshooting old systems, say 14 years and older. This particular poster is a well known and respected expert on Honda Odyssey’s. He said two things which really got my attention. First, old AC components have a high failure rate and second, vacuum tests do not mean much on an old system because sometimes old seals will hold vacuum but not pressure. This is particularly true on a compressor. I have always bought new cars and driven them 15-20+ years. My current car is a 21 yo Avalon. The only failure I have experienced was a rock puncturing a condenser. This happened on my Avalon 13 years ago. Was interested in your experience. Should I be expecting the AC on my 21 yo Avalon to crater sometime soon? Thanks.

  • #2
    Depends on where you live and what kind of driving you do. Condensers are right out front, and get the worse of whatever the road can give it. The chlorides they use to de-ice the roads in winter can really ruin a condenser even if it doesn't leak. The old tube and fin condensers can corrode between the tubes and fin joint and stop conducting heat out to the fins.
    Condensers are one issue, tubes are another, they can corrode through and be hard to spot as they are often buried.
    I run stuff that is coming up on 40 years old. It is in a heavy truck and is run in the norther states. I just had to replace the original evaporator due to corrosion getting to it. It's location is in the cab right over the passenger side steer tire, so easy to see how the chlorides got to it.
    Most compressors in the past used face seals to seal the compressor shaft. These type seals do not ride directly on shaft to seal like a wheel seal does. The count on the oil in the compressor making a tight seal between two plates one rotating with the shaft and one stationary with the case. I have seen some newer seals that ride directly on the shaft. These can give a tighter seal at first, but can wear a groove in the shaft over time.
    Hoses are another thing that don't last forever. Heat and time can degrade them and they can be hard to tell they are leaking. I had one, that would sound like someone popping a bubble-gum bubble every once and a while. The refrigerant had made it past the inner liner and was seeping through the body of the hose, when it reached the outer cover, it would form a bubble that would eventually pop the outer cover. If you didn't see it when it happened it would look like nothing was wrong.
    On this truck I have replace most all of the hoses, the condenser, evaporator, drier ,Tx valve. and a compressor Not all was done at once and for a commercial vehicle will millions of miles (literally) on it that is to be expected.
    With a car, I would keep track on how many time it needed a recharge. The most important thing is to never run the compressor low on oil. Since refrigerant oil is soluble in the refrigerant, every time it loses charge some of the oil is carried with the escaping refrigerant. Every 2nd time it needed a re charge I would pull and drain the compressor of oil, and re fill with a new oil in the amount called for. Some of the oil will remain in other components, but a slight over fill of oil is better than starving the compressor.
    All that being said, a 20 or 30 year old system should hold vacuum. Shaft seals would be something I would look at if it had trouble hold a charge. I wouldn't expect the system to "crater", if it were to die it would be from a 1000 little cuts, you would start chasing problems that one you fix one, another pops up.
    That being said when I sold my '94 car when it was in its mid 20's it had cold A/C and only had one condenser replacement as its only major problem over the entire time I owned, it.


    • #3
      Oh and to older components having a high failure rate. I needed a compressor to replace a rebuilt that failed (rebuilt compressors have a bad rep for failure) I bought a compressor from a 1960's truck, changed the oil to pag and installed a different clutch. It is going on 50-60 years old and working fine!
      Since my bad experience buying a rebuilt, I have since purchased the special tooling to rebuild my own. Normally I buy used and re seal, but that time I needed one right away and tried a rebuild. It lasted only two seasons. Once I got it apart and looked at how it was assembled by the rebuilder, I was surprised it lasted two seasons.
      Newer aluminum compressors don't last like the old behemoths made of cast iron do, but 20 years shouldn't be a problem.


      • #4
        We've had a 1998 Frontier since 2004, bought at 100K miles and just passed 250K.

        First AC failure was a pinhole in the high-pressure rubber line, on a 119F afternoon and I discovered a bad fan clutch at that time too. Last summer, I removed an AC clutch shim because the AC clutch was occasionally slipping. And the AC belt idler pulley bearing went bad once. That's it.

        2004 Frontier, same setup, 103K miles: AC compressor seized in 2018, replaced compressor, condenser, and drier.


        • #5
          That thread will show some of the problems you can find on an old system.


          • #6
            Thx for the great responses. Very helpful. Never thought about the rubber hoses.


            • #7
              If contemporary automotive A/C systems were as good, simple, and reliable like those of 15-20 or more years ago, we would be out of busienss. I'm yet to know a new car, any brand you want, with a system quite like that found in, say, a 1999 Tahoe or F150, Toyota, Nissan, you name it. We just delivered a few minutes ago a 1999 Tahoe. Its problem was a leaky service port. The newest examples, on the other side, were a 2013 Camry (evaporator), 2017 Explorer (compressor), 2015 Sentra (compressor), 2015 Ram (evaporator), among many others. My advise: don't touch unless you note some abnormality. Just turn the compressor on 5 minutes per week in winter.