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Testarossa AC Dryer Freezing

Discussion in 'Technical Q&A' started by swamthing, May 3, 2021.

  1. swamthing

    swamthing Rookie

    Apr 28, 2021
    7
    Full Name:
    Jonathan Clark
    AC seems to be flowing at startup and blowing cold. After a few minutes the dryer starts to freeze at it's base and flow stops. My AC compressor does run and I see flow in the sight window until it freezes.

    Thoughts on where I start before a dealer tells me they have to pull my dash apart?

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  3. wmuno

    wmuno Karting
    Silver Subscribed

    Dec 24, 2007
    141
    Wilmette, Illinois
    Full Name:
    Bill Muno
    Freezing in the evaporater (and dryer) is usually caused by low refrigerant. Recharge the system and see if this solves the problem. If it does, the next step would be to determine if there is a slow leak. If an obvious leak can not be found, there are sealers that can be added to the system to stop pinhole leaks.
     
  4. flash32

    flash32 Formula 3

    Aug 22, 2008
    2,468
    Central NJ
    Full Name:
    Dominick
    My bet considering on high side a blockage in dryer


    Test a few things

    Are lines coming into dryer hot ?

    Are lines leaving dryer colder ?

    If yes ..dryer has a blockage and acting as an orifice

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  5. raemin

    raemin Formula Junior

    Jan 16, 2007
    808
    Lyon (FR)
    Full Name:
    R. Emin
    Some debris are probably preventing the expansion valve from properly stoping liquid refrigerant from escaping the evaporator.

    Check also that the pressure switch on the drier is properly operating.
     
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  6. raemin

    raemin Formula Junior

    Jan 16, 2007
    808
    Lyon (FR)
    Full Name:
    R. Emin
    For the record, the refrigerant enters the evaporator in liquid form, then should "evaporate", and finally gets pack to the compressor (through the drier/filter).

    When it escapes the evaporator, if it is in liquid form, there is a risk to seize the compressor. Sot there is an expansion valve at the exit of the evaporator. This is basically a "sensing bulb" that expands when the refrigerant is too cold (i.e liquid). This expansions closes the system, as a result this modifies the pressure untill the pressure switch kicks in and stops the compressor.

    If your drier is too old, it is possible that some desiccant particles have escaped from the filter and found their way up to the valvle and prevent it from properly closing.

    If your AC does have a thermo-switch (snowflake switch with a fin inserted in the evaporator), then you can try to reduce the AC input and see if this solves your issue temporarily (thermo switch stops the compressor when the evaporator has riched a given temperature, if switch is low enough this kicks in before the expansion valve). In this case you could invest in a new dryer and let the AC work until the debris are all captured again by the new filter.

    This is based on my knowledge of the 400i system, so your mileage on the Testarossa may vary.
     
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  8. flash32

    flash32 Formula 3

    Aug 22, 2008
    2,468
    Central NJ
    Full Name:
    Dominick
    #6 flash32, May 3, 2021
    Last edited: May 3, 2021
    The dryer /sight glass is on the high side on the testarossa then to the expansion valve ..so not sure if your description fits

    It is liquid going in and out of the dryer /sight glass .. The issue here is that it is turning to gas within the dryer ..hence blockage/restriction within the dryer if lines coming in are hot and outlet is cooler

    If lines are cool both sides - most likely a low refrigerant

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  9. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    20,361
    socal
    Low hanging fruit DIY style, sans real diagnosis is to evacuate, cook dryer in oven 250F for an hour, refresh orings in system, draw vaccum for 1+ hours. Then if vac hold recharge. This involves very little of your time while you do other things in the garage. Now doing it right is a much longer process.
     
  10. windsock

    windsock Formula Junior
    Rossa Subscribed

    Nov 29, 2006
    564
    Arlington, Washington

    The drier in this system is on the high side after the condenser so it should see nothing but liquid refrigerant. This is likely due to a plugged or restricted filter causing a pressure drop in the drier assembly. Now the next question is what is causing the restriction. Best case the drier bag came apart, worts case the compressor is failing and sending metal through the system. Remove and open the drier and inspect for debris.
     
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  11. raemin

    raemin Formula Junior

    Jan 16, 2007
    808
    Lyon (FR)
    Full Name:
    R. Emin
    If the dryer is on the high side, I would not try to resurect it in the oven, and use instead a brand new one (not new old stock "with glass" ).

    The pressure switch that is built in the dryer (I see to wires on the pic) may also have been damaged. Would not take a chance.

    When was the dryer last replaced?
     
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  13. swamthing

    swamthing Rookie

    Apr 28, 2021
    7
    Full Name:
    Jonathan Clark
    I’m not sure. Trying to look through history. They did some AC work 5 years ago then a recharge 3 years ago.
     
  14. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    33,604
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    Ferrari recommends changing the drier/filter every 2 years on models up through the 575s.
     

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