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AC - If compressor and fan are running, refrigerant is full, but the air is cool but not cold enough

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by yossi, Jun 8, 2021.

  1. yossi

    yossi Junior Member

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    2008 - If compressor and fan are running, refrigerant is full, but the air is cool but not cold enough, what else can it be? Cabin air filter is new, AC button is on, temp set to LO, air to recirculate. The temperature of the air coming out of the vents on a 75 degree day is around 65-66, on an 85 degree day, air temp is around 70. Dealer said the charge is full. I am going to take it to a local guy to recheck but if they also say refrigerant is full, what else can I check that might be causing the air to be cooled but no where near what is expected?

    The sight glass shows some "turbulence" but I know that is not really a solid indicator. the low pressure hose feels cold, but not ice cold and there is no condensation forming on it
     
  2. rjparker

    rjparker Tu Humilde Sirviente

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    Its not full with bubbles in the sight glass and very likely has air in the system from a diy charge where the can's hose was not vacuumed or purged. Needs a pro vacuum and proper refrigerant weighed in after a new filter dryer is added. On a variable speed compressor weighing in is the only way. Ensure the ac specialist has worked on electric driven variable speed compressors.

    Before doing anything, the pro should use dye and or an electronic refrigerant detector and look for the leak. When found it should be repaired. Running these compressors with low refrigerant is very bad for its seals and bushings. Plus a leak will just lose the refrigerant again.

    The pro can use digital gauges to monitor pressures to ensure the compressor is generating proper head and can use temperature clamps with the digital gauge to calculate realtime superheat and subcool. A combination of factors derived from the data can determine if there are clogged coils, txv, dryer or failed compressor. Generally he won't need to go this far once he does the initial vacuum, leak check, dryer replacement and recharge.
     
    #2 rjparker, Jun 8, 2021
    Last edited: Jun 8, 2021
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    In addition to everything that rjparker said, you could have dirt and debris restricting airflow through the condenser. Or a problem with the evaporator temperature sensor. One time had a condenser fan that was wired backwards. Could be anything.

    First step is to have a fully equipped professional check the system for leaks, recover and recharge the system by weight, then evaluate function by system presures and temperatures.

    Posted via the PriusChat mobile app.
     
  4. yossi

    yossi Junior Member

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    So I tried to do some diagnosing and stared by closing all four vents and then opening one at a time. I discovered that the two right vents, while not ICE cold, are definitely colder than the two left vents. So is that a charging issue or reflective of some issue with the internal flaps and doors that mediate the cold/warm air?
     
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    It is an indicator that system charge is (probably) low- there isn't enough liquid refrigerant to fully "flood" the evaporator core so half of it can't get as cold. But that is a guess.

    Posted via the PriusChat mobile app.
     
  6. TMR-JWAP

    TMR-JWAP Senior Member

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    If you can see turbulence, then you see refrigerant bubbles. In the (7) Gen 2s I've looked at this summer, a well running AC system has ZERO visible turbulence in the sight glass. The flow is 100% clear liquid refrigerant and can't be differentiated from having no flow at all. The bubbles are not going to be air if the system has never been opened. For continuous "air" bubbles to show up under that much pressure would mean a huge amount of air was injected into the system. A little bit of charge or undercharge makes a big difference in the system.

    Just my unprofessional DIY real life observations.
     
  7. edthefox5

    edthefox5 Senior Member

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    Yep I had rushing turbulence in my sight glass ac was cool not cold.
    Ac shop says you have a leak in the evap coil.

    They replaced ecoil ac now freezing and sight glass clear.
     
  8. yossi

    yossi Junior Member

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    What did they charge to replace the coil?
     
  9. rjparker

    rjparker Tu Humilde Sirviente

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    Until you have it diagnosed it is a guessing game. Evap replacements are major since the dash has to come out and generally a new txv and filter dryer will be installed with the new evap coil.

    But it could be a slow leak anywhere that could be fixed or you might get by another season or two with a good evacuation and weighed in charge.
     
  10. TMR-JWAP

    TMR-JWAP Senior Member

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    or you could get by for 10 years by adding a couple ounces each season...you just never know because every situation is different.
    What you do know, is that you do not have a significant leak. If it was 'significant, there would be nothing visible in the sight glass, since all the refrigerant would be gone. AC performance that has slowly degraded over the period of a year(s) + and can be rectified with a $5 can of R134 is not what I would consider a significant leak. I would be very hard pressed to invest 4 digits to make a repair in that situation.
     
  11. edthefox5

    edthefox5 Senior Member

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    $1050 out the door.