1979 308 GTB A/C wild and strange issue | FerrariChat
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1979 308 GTB A/C wild and strange issue

Discussion in 'Technical Q&A' started by Ted, Sep 5, 2023.

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  1. Ted

    Ted Rookie

    Nov 3, 2003
    18
    Azle Texas
    Full Name:
    Ted Gage
    #1 Ted, Sep 5, 2023
    I've just added Freon to the car since 1980. This time I decided to pull a good vacuum and start over with new 134a. Big mistake. I can test the system with nitrogen at 200 psi with gauges attached, and it will hold that pressure for days with ZERO psi loss.

    However, I cannot pulll a vacuum. Stop the vacuum system, close the valves, and the pressure goes back to zero in a minute.

    Any suggestions? Next, the plan is to remove the connections to the compressor and loop it back to high and low side. This should indicate that the vacuum leak is in the compressor or somewhere in the system.

    What a bummer, This AC has worked great for 43 years. Any body ever had this happen?
    Thanks in advance.
    Ted
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,794
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Sep 5, 2023
    I think that you can only conclude that you have some sort of flaw that allows flow in one direction, but seals itself when the flow (the pressure differential) is in the opposite direction. As you noted, isolating sections/components, and retesting, seems the only way to figure out where the trouble is located.
     
  3. raemin

    raemin Formula 3

    Jan 16, 2007
    2,339
    Lyon (FR)
    Full Name:
    R. Emin
    #3 raemin, Sep 6, 2023
    Last edited: Sep 6, 2023
    The pressure seal inside the ASPERA compressor is not designed for vacuum. As a simple test you can tap the inlet port and turn the compressor in reverse you will immediately hear the vaccuum leak.

    So just pull some moderate vacuum, and immediately refill.

    Hope you fully changed the oil of the compressor before the R134 switch. Otherwise R416 would be a safer bet. It's basically R134 with a bit of hydrocarbon gas meant to prevent the old oil residues from solidifying.
     
  4. raemin

    raemin Formula 3

    Jan 16, 2007
    2,339
    Lyon (FR)
    Full Name:
    R. Emin
    #4 raemin, Sep 6, 2023
    If your ASPERA compressor was refurbished with a York seal, this would make maters even worse as the new type of seal is thinner (the retaining spring applies even less tension on the seal against the crankcase). The York seal holds the pressure though.

    These were made under York licence, but are not York: your AC guy should not expect these compressors to hold vacuum like a regular York 206.
     

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