R134a A/C system charging --- general question | FerrariChat
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R134a A/C system charging --- general question

Discussion in 'Technical Q&A' started by finnerty, Sep 21, 2015.

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  1. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,406
    #1 finnerty, Sep 21, 2015
    The "rule of thumb" as a general indication (visual verification) for charging the old R12 systems was that the system was fully charged when you could see that the fluid running through the sight glass on the drier/receiver was clear and totally free of bubbles / foam ---- if it wasn't completely clear and had any bubbles / foaming, it was not fully charged.

    Does this still hold on the R134a systems ? Or, is some foaming / bubbles normal even on a fully charged system ---- and it is not possible to eliminate all of it without over-charging (which of course you do not want to do) ?
     
  2. PAP 348

    PAP 348 Ten Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2005
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    Mount Isa, Australia
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    #2 PAP 348, Sep 22, 2015
    Some people say that you don't use the sight glass in R134A systems to gauge whether the system is full or not.

    Some people say that it doesn't matter and you can use that sight glass to tell.

    From my experience (12 yrs of servicing and repairing a/c systems), I reckon you can use the sight glass to tell if an R134A system is fully charged or not.

    I can deal with some very minor bubbles in there, but for the most part I use pressures to tell if the system is right and the 'feel' test on the low side a/c pipes.

    But to answer your question, it's a yes from me. You can use the sight give you an indication of what is going on there.

    But you will definitely have to put some gauges on the system to get a better idea of the a/c performance.
     
  3. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,406
    #3 finnerty, Sep 22, 2015
    Thanks PAP ---

    Don't worry, I'm definitely using a gauge (but only on the low "suction" side) as well to set it.

    But, what strikes me as odd is that with the system currently charged to within, but on the low end of, the pressure range for the given ambient temperature, there is still quite a bit of foaming in the glass.... the "feel" check passes, and the vents are blowing good cool air.

    I just wonder if I should keep adding more charge until the foaming is gone, and the pressure reaches the high end of the range, or leave it as is ??? I am nervous about the possibility of overcharging more than anything else, because that can blow hoses and damage the compressor.
     
  4. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    Brian Crall
    #4 Rifledriver, Sep 22, 2015
    It has been a long time since the industry has suggested the use of the sight glass to gauge Freon charge. We have used weight of charge for a long time and in my experience with correct weight and correct pressures, bubbles are the norm.

    Having said that, in my experience, at least with the Ferrari's that had 134a as the factory fill the suggested weight was not enough to get full efficiency from the system.

    As for retrofit situations, I don't do them. I still use R12.
     
  5. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #5 Steve King, Sep 22, 2015
    I went with the 80% charge rate and then used the gauges vs pressure vs outside temp to 0 it in. The sight glass is pretty useless as even with a full 134a charge there is still bubbles in it. Use the gauge and outside temp. guide. The best I could do was 40* at the center vent. As we all know the big windshield makes the car a greenhouse so the system is marginal in 95* temps but works good at 80*
     
  6. PAP 348

    PAP 348 Ten Time F1 World Champ
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    #6 PAP 348, Sep 22, 2015
    Last edited by a moderator: Sep 7, 2017
    Don't stress too much mate, there will always be some bubble ins in the sight glass even when it near to fully charged the system.

    Just leave it be, run with the pressures and the feel test.

    A perfect world is where you weigh the refrigerant as Brian just mentioned. That's what I normally do also and just did to my Ferrari two days ago.

    Put the exact 900gram charge of R134A into. I haven't checked the system yet as I don't have any power to the a/c clutch, going to sort that problem out today or tomorrow.
    Image Unavailable, Please Login
     
  7. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,406
    #7 finnerty, Sep 22, 2015
    Indeed, fully emptying and then filling with the system capacity spec by weight amount is the "proper" way to go. But, I was just topping off, and I do not have the vacuum equip to evacuate the system / leak check etc. which, of course, a professional shop would ( I suspect it may even be a law in most states ? ) do.

    It was low about 60% of total capacity on a car that has not had its a/c serviced ever since new (MY 2003), so I suspect this is normal leakage / escape over the course of 12 years ---- I don't suspect any crucial leaking going here, so I just decided to top it off (used 134a with sealant additive just to be sure though).

    Thanks again everyone !
     
  8. Wade

    Wade Three Time F1 World Champ
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    Mar 31, 2006
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    #8 Wade, Sep 22, 2015
    That's what I did (for now).

    http://www.ferrarichat.com/forum/143938182-post1.html
     
  9. PAP 348

    PAP 348 Ten Time F1 World Champ
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    #9 PAP 348, Sep 23, 2015
    Very good!

    I just completed another a/c course two weeks ago.

    A/c hoses are actually porous and they all leak a little over time.

    My Tafe teacher actually said the seal up products we have these days are very very good!

    He has used it plenty of times and it has fixed the nasty leaks that are very hard to find.

    You will be fine putting that sealant in anyway.
     
  10. Fast Rev

    Fast Rev Rookie

    Feb 4, 2007
    29
    Linthicum, MD
    #10 Fast Rev, Sep 23, 2015
    May I suggest that you feel the bottom coil of your condenser? When properly charged, with moderate temp and humidity, the bottom of the condenser should be filled with liquid and feel cool to the touch.
    With 134a the sight glass is meaningless with the exception of the bronze ring indicating water in the system. 134a is charged by weight, not volume, and confirmed with gauge readings.
    If anyone is interested, I have a powerpoint presentation that deals with 134a conversion. It covers SAE specs for hoses, barbs, and safety concerns with 134a. Just drop me an email and I will send it to you.
     

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