Convert Air Conditioner from R12 to R134

Discussion in 'Maintenance Bay' started by BGF_Yankee, Jun 1, 2015.

  1. BGF_Yankee

    BGF_Yankee Line Up and Wait

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    What is involved in this on my (PA32R) aircraft? I see all kinds of information online about this on cars, but not seeing much for aircraft.
     
  2. docmirror

    docmirror Touchdown! Greaser!

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    I don't have an answer to your question, but I can bet it's far, far more costly then just servicing the unit with R-12. Get some R-12, replace as many seals as you can, then pressure test, and fill-er-up. I would forget R-134a for aircraft use, but that's just me.
     
  3. BGF_Yankee

    BGF_Yankee Line Up and Wait

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    Honestly, I know very little about this part of my aircraft's systems. I was told that R12 was not easy to get. Forgive my idiocy, but is this not true?
     
  4. Clark1961

    Clark1961 Touchdown! Greaser!

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    Nobody is making R-12. There may be some recycled R-12 around. I've got some in an old freezer I'll sell you at a horribly high price.

    I think that I'd convert a system to propane before I'd convert it to R-134a.
     
  5. BGF_Yankee

    BGF_Yankee Line Up and Wait

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    ...so then what is everyone out there doing that has an air conditioning system on their aircraft if they need a recharge??
     
  6. Archammer

    Archammer Cleared for Takeoff

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    As far as my limited knowledge is, changing to R134 is surprisingly simple. You just have to replace the orifices in the system, and then charge with R134.

    My understanding is that there is no other changes required to tanks, lines, or other hardware. I don't believe the orifices are expensive, can be self installed and signed off by your A&P. They are long looking tube filters that slide into the lines in certain areas. (There may be others that aren't in a car system)

    I would ask the A&P you use first and go from there.
     
    Last edited: Jun 1, 2015
  7. docmirror

    docmirror Touchdown! Greaser!

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    Well, there's plenty of R12 outside of the US, and I can get as much as you want. The question you asked is just about conversion, not cost. There's no shortage of R12 if you ask around some.
     
  8. tyndall

    tyndall Pre-takeoff checklist

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    R134a has a smaller molecule that seeps through old style hoses and seals. In other words, if your system has a minor leak with R12, it will be a major leak with R134a. Then there's the fact that 134a doesn't cool as well and there may be a compatibility problem with the compressor oil.

    R12 is around. Stay with it.
     
  9. docmirror

    docmirror Touchdown! Greaser!

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    Don't forget that switching to barrier hose in an aircraft prolly requires an STC. Don't know if it would qualify for a 'minor change' on a 337. The FAA has gotten super stingy about the 337 process, but I guess it could be tried. It would be an owner produced part, and the hose would have to conform to the orig spec, or better. Even though barrier hose is a better quality, does it meet/exceed the orig spec for the old hose? This is where changing anything on a plane gets iffy.
     
  10. docmirror

    docmirror Touchdown! Greaser!

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    R-12, 12Oz cans ~$40 per can, as many as you can carry. PM me for shipping, we take paypal. Prolly takes 3-4 cans, so adding in the seals the whole job can be done for $200 in materials, and whatever labor the A&P wants to get for repl the seals and pumping it down, then a pressure test.

    Way, way less than converting I would bet.
     
  11. bnt83

    bnt83 Final Approach

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    Just saw it happen on a Lear 60. New evaporators, new expansion valves, new receiver dryer, new pump, all new seals and new hoses via a pricy STC.

    I'm guessing the STC was written to basically overhaul the system to ensure trouble free operation during the warranty period.
     
  12. bnt83

    bnt83 Final Approach

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    First you need to know who's air conditioner you have.

    Was it a factory installed one?
    Was it a factory installed STC made by someone else?
    Was it a STC installed in the field?

    After you determine that, then I'd probably call a Piper dealer while near or sitting on a toilet.


    No matter which one it is, hopefully they still support it and a conversion kit is available. If its working well now, I would plan on buying the kit and pull the trigger when it quits. Lead times for parts is pretty unpredictable where I work so you might want to order them a lot sooner.
     
    Last edited: Jun 1, 2015
  13. SCCutler

    SCCutler Administrator Management Council Member

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    Have a comprehensive leak check performed and repair all leaking parts (odds are, new seals will do it); then recharge with R12. The supply may be diminishing, but there is plenty around for a while yet.

    Converting to 134 is not trivial.
     
  14. BGF_Yankee

    BGF_Yankee Line Up and Wait

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    It's a factory Piper air conditioner on my Lance. I'm just scratching my head about the whole thing. Local shop tells me that R12 is hard to get. I call the shop that tried to charge it when I first got the plane (before repairs) and he told me he just charges it with R134, but that he has adapters to fit the current valves. I really just don't know that much about it like I said. Trying to get some education here.
     
  15. bnt83

    bnt83 Final Approach

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    http://www.conversionairkits.com/2643.html


    http://www.ainonline.com/aviation-n...rsionair-kit-upgrade-air-conditioning-systems

    PA-32-300 32-40853, 32-7340056 AND UP 98320501-001 $5,031 USD

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    PA-32RT-300T 32R-7887001 THRU 32R-7987146 98320508-001 $5,031 USD

    [​IMG]
     
    Last edited: Jun 1, 2015
  16. bnt83

    bnt83 Final Approach

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    There may be other conversions out there than that one.
     
  17. docmirror

    docmirror Touchdown! Greaser!

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    If you PM me, I'll get you as much R-12 as you want. I can prolly get you the hose seals too.

    :confused:
     
  18. Arrow115

    Arrow115 Pre-takeoff checklist

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    Mine has been inop since I got it. I haven't been able to find a mechanic who is interested in working on the factory ac.
     
  19. docmirror

    docmirror Touchdown! Greaser!

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    Schedule it by PM, and bring it up to Denton. We'll get you filled up and going. We've got a doer of ~30Lbs of R-12. If it doesn't pass the pressure test, you'll have to either leave it, or come back another time.

    The biggest issue for aviation AC systems is the compressor seal is the same as used on autos. If they aren't used often, the seal dries out and the freon just leaks away. Aviation is even worse with the low use cycle.
     
  20. Arrow115

    Arrow115 Pre-takeoff checklist

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    PM sent. Thanks!
     
  21. mtuomi

    mtuomi En-Route

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    What's the general consensus? Would you rather take your plane to a place who know everything about AC systems but are not an A&P (technically illegal, or is it?), or take it to an A&P who has no clue about AC systems (legal or is it if no proper paperwork for handling R12/134A?)
     
  22. docmirror

    docmirror Touchdown! Greaser!

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    Work by anyone on an aircraft can be, and often is supervised directly by an A&P. I do almost all my own work on my plane, and my logbooks are current and legal.

    There's no requirement that I'm aware of that an A&P need a HVAC cert for handling refrigerants to supervise servicing an aircraft AC system. There's a book, with service instructions. Follow that and what's the problem?
     
  23. drotto

    drotto Cleared for Takeoff

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    My father did this to his plane and it has a few hiccups in the process. Well granted some may just be that his AC system was a leaky mess, but almost there. As long as the rest of the system is solid it should be fairly smooth. One thing to watch out for, the new 134 systems may use a different size belt than the one that is currently on the plane. The new 134 systems are STCed but are not recognized by Piper. On his PA32 the belt size on the engine pulley is either 1/8 or 1/4 different from the new compressor pulley. It took the mechanic some tinkering to get them to be happy together. The mechanic debated getting a new engine pulley made (Piper does not have an approved one), but it would be a bunch of time plus the 337 paperwork. Eventually, they moved to a belt that is sized for the larger of the two pulleys and it seems to work. When they attempted to use the smaller belt size, there was twisting of the belt, and he was afraid it would break over time.

    At this point in his plane, basically all that is left of the original system is the tail condenser coil. He was forced to replace basically everything.
     
    Last edited: Jun 3, 2015
  24. Gerald K4NHN

    Gerald K4NHN Filing Flight Plan

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    I'm not an A&P, but I do AC work on cars. Most conversions from R134 and R12 usually are not 100% the same preformanc as before. A lot is by because the person doing it doesn't really know AC work like they should... My one comment is if at all possible stay with the R12, it's still around, and one last comment, "There Are No Short Cuts To AC Work" do it right the first time.

    Gerald K4NHN
    Cayce, SC
     
  25. bnt83

    bnt83 Final Approach

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    Same observation on a Learjet.
     
  26. bnt83

    bnt83 Final Approach

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    Seems like some have nothing but trouble with them. They seem like a pretty simple system to fix to me.

    My car is 13 years old and I don't believe the AC has ever been serviced. Still works.
     
  27. jesse

    jesse Touchdown! Greaser!

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    I would stick with R12 for sure. Going to 134a will involve a lot and likely won't perform nearly as well. You can buy R12 on eBay although it isn't cheap. So make for damn sure you know all leaks are fixed.

    If I were really desperate to find R12 and money were a problem I'd just look at junk cars on Craigslist that I know would have R12 then I'd give them $10 or something if they let me take the R12 out :)

    I'm not sure how many A&P(s) are AC experts so if it were mine I'd be doing it all myself and finding someone to inspect and sign off.
     
  28. Clark1961

    Clark1961 Touchdown! Greaser!

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    Auto air conditioners have done a lot better since they started running them with the defroster along with the usual air cooling chore. The year-around operation keeps the oil distributed which helps the seals.
     
  29. jesse

    jesse Touchdown! Greaser!

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    I had a bunch of trouble with the AC on my F150. I think I put about four compressors on that thing in two years before I finally pulled my head out of my ass and quit buying compressors from Autozone. Ordered the OEM compressor off the internet and haven't had an issue since.
     
  30. drotto

    drotto Cleared for Takeoff

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    The leaks became the problem on the Saratoga. First they tried just recharging it, but the ac failed. Then they replaced a manifold in the system which had a leak, and it worked before failing again. This time when the system failed the compressor froze up completely and the were forced to replace it. Thus the 134 conversion. They though they had the leaks, but again the system failed and the new compressor was ruined. After numerous attempts, repairs, and three compressors, a new mechanic during annual pulled out all the original rubber hosing that ran from the nose to the tail. He pressure tested just that and found leaks. He then replaced all that old rubber with copper lines. Then he had the belt sizing issues, but finally the system seemed good. The plane is taken up again, and the switch which controls the door on the bottom of the plane fails, so the ac will not work without that door open. The mechanic rechecked the system, all seems good, just waiting on the switch now.
     
  31. bnt83

    bnt83 Final Approach

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    Wondered why they did that.
     
  32. Bill

    Bill Touchdown! Greaser! PoA Supporter

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    American cars ran the compressor on defrost since about forever. At least this was true in my father's early 70's Detroit barges. The last time I owned a Japanese car in the early 90's it wasn't automatic, one had to turn on the compressor (ac) if they wanted it.
     
  33. Bill

    Bill Touchdown! Greaser! PoA Supporter

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    Dried air removes fog/mist faster.
     
  34. jesse

    jesse Touchdown! Greaser!

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    Mostly because AC systems make great dehumidifiers. This is why having massively oversized AC systems is a bad idea, if they don't have to run for a good amount of time to do the needed cooling, you won't get the benefit of the dehumidification and will end up "cool" but in humid air.

    This is very noticeable in a car where the AC system is broke and you're trying to defrost.

    A household dehumidifier is basically an air conditioner that uses the excess heat from the process to reheat the cooled air instead of dumping the excess heat outside your home.
     
    Last edited: Jun 3, 2015
  35. docmirror

    docmirror Touchdown! Greaser!

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    Yup, it was specifically done to help keep the seals and o rings in the system lubed during cold months when defroster use is typical. This is one of the main problems with planes that sit for weeks at a time.
     
  36. jesse

    jesse Touchdown! Greaser!

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    Well that plus the defrost works way way way better with the AC system removing the humidity.
     
  37. mtuomi

    mtuomi En-Route

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    There's also the low and high pressure switches on the AC system. You'll find the compressor clutch doesn't actually engage when it's cold enough.
     
  38. Henning

    Henning Ejection Handle Pulled

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    Reclaimed and NOS R-12 is still pretty available, though it is expensive, and requires a license to work with (simple online test when I did it, read the pamphlet and took the test, done.) Auto recycling yards used to be the best source, but not many R-12 cars left.

    The R-134 conversion itself is simple enough, the systems are all built with common automotive components so the drier and o-rings will be no problem. The question is one of legality and if the system has been subsequently certified for the 134a conversion. Even without, this may still be doable through the FSDO. Get the component numbers and any industry standard certification numbers for them and you and your IA fill out a 337 proposing what you intend to do. Aircraft mods are one place the "It's easier to ask forgiveness than permission" rule does not apply. Get approval before you change it out, but changing it out itself is not a big deal. You will lose some cooling performance though.
     
  39. Gerald K4NHN

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    With a leak you also loose oil, faster the leak usually more the lost of the oil too. And if that oil isn't replaced the compressor keeps going out. Anytime there's a leak the only way to know how much oil is left in the system is to flush it out totally and start new with the correct amount of oil. All leaks have to be fixed or you'll never get the AC to operate correctly. A slow leak just takes a little longer before you're back to ground zero again to start it all over again. To much oil makes for reduced cooling, to little oil equals a burned up compressor. Remember, there's no short cut to AC work. Do it right the first time.
     
  40. bluerooster

    bluerooster Pattern Altitude

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    Removing it, and carrying more than a toothbrush while on vacation. :D