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512TR A/C Pressure Question

Discussion in 'Technical Q&A' started by LP400S, May 7, 2007.

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  1. LP400S

    LP400S Formula 3

    May 18, 2002
    1,223
    West Coast
    #1 LP400S, May 7, 2007
    My car is only blowing 60 degrees at the vent sometimes 55. The outside air temp is 85 degrees. Does not feel as cold as it used to. It used to get really cold even when it was over 100 outside.

    I hooked up the pressure gauges and the low and high side keep fluctuating up and down. The low will be at 28 psi and the high 225 psi then it goes down to low side 14psi high 180psi. Should the readings be going up and down while the car is running ? The system just got filled with R12. Any thoughts on what these readings mean? Is it normal?Thanks
     
  2. WaltP

    WaltP Formula 3

    Nov 1, 2003
    1,512
    Cape Canaveral/Atlanta
    Full Name:
    Walt P
    #2 WaltP, May 7, 2007
    Sounds low on R-12 and on the verge of freezing up.
     
  3. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    Dec 7, 2003
    16,460
    Winston Salem, NC
    #3 Ricambi America, May 7, 2007
    Last edited by a moderator: Sep 7, 2017
  4. WaltP

    WaltP Formula 3

    Nov 1, 2003
    1,512
    Cape Canaveral/Atlanta
    Full Name:
    Walt P
    #4 WaltP, May 8, 2007
    Last edited by a moderator: Sep 7, 2017
  5. pippo

    pippo Formula 3

    Sep 25, 2005
    1,913
    FL
    Full Name:
    pippopotemus
    #5 pippo, May 8, 2007
    Cant help you re the pressure issue, but I can say with some confidence that cooling temp difference is normal if the evaporator is cooling INCOMING (not outside he car air) about 30 deg F. Thats GOOD! With R134a, about 25deg F. Incoming air is air being sucked in by the cooling unit blower motor attached to the evap. If temp is 100 F outside, you cant expect ac to cool to 55 or even 60 deg F.
     
  6. Mark 328

    Mark 328 Formula Junior

    Nov 6, 2003
    510
    Orange, Ca
    Full Name:
    Mark Foley
    #6 Mark 328, May 9, 2007
    Could the humidity be different? 85 with high humidity might be harder to cool than a dry 100.
    When checking the pressures is the car idling? Generally the engine needs to be running at about 2,500 RPM for the pressures to stabilize (this is probably in the shop or an A/C manual). The compressor needs to be putting out enough volume so that the system is not strained (pressure drop) when the expansion valve opens.

    Mark
     

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