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Techstream readings, healthy vs. sick A/C

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by pasadena_commut, Sep 14, 2022.

  1. pasadena_commut

    pasadena_commut Senior Member

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    I don't have any of the cool A/C instruments that Lech uses in his videos, but I do have a working Techstream. Which of the A/C related values Techstream can show give the best indication of the A/C's location on the "working perfectly" to "going to blow up in 5 seconds" spectrum?
     
    #1 pasadena_commut, Sep 14, 2022
    Last edited: Sep 14, 2022
    lech auto air conditionin and SFO like this.
  2. ChapmanF

    ChapmanF Senior Member

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    Not much of anything I know of in Gen 2. That's why A/C shops have the cool instruments.

    In Gen 3 there's a high-side pressure reading you can see, but without other measurements even that doesn't tell you a lot.
     
    #2 ChapmanF, Sep 14, 2022
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  3. lech auto air conditionin

    lech auto air conditionin Senior Member

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    I think I have a older video about six years ago back when I first got my 2012 Prius C using tech. stream on my personal vehicle.

    A lot of vehicles you actually do not need gauges if you have the factory scanners they literally show you all the pressures and temperatures. No need for gauges. On these type of vehicles you just need a cylinder of refrigerant a scale and a single hose.

    Everything Else you can do with your fingertips feeling temperature differences and vibrations just feeling around using your ears no tools needed.
     
    #3 lech auto air conditionin, Sep 15, 2022
  4. lech auto air conditionin

    lech auto air conditionin Senior Member

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    Actually I was wrong it was 10 years ago


    The video and the sound is so bad can’t remember what iPhone I was using or if it was an android
     
    #4 lech auto air conditionin, Sep 15, 2022
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    On a Gen2 you have maybe compressor RPM and evaporator temperature (hey, the compressor is spinning but it's not very cool!). There is a pressure switch input- useless for health check on a working system. No high side pressure sensor on a Gen2.

    You really need a pressure gauge set and a good visual inspection to tell much

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Sep 15, 2022
  6. pasadena_commut

    pasadena_commut Senior Member

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    Ah, too bad about the techstream limitations. The thing is, after the dealer finally diagnosed and replaced the leaking evaporator problem, which took way too may visits, I was left with an uncomfortable feeling that they just were not very good at Prius AC work. The AC has been working since then, although lately I have the impression that it is just a hair less cold than it used to be. So I have a nagging suspicion that it would be a good idea to find a second, competent, AC shop and have them verify that it has the right amount of refrigerant and no air or water or other issues. But I have an even bigger nagging suspicion that a lot of "car AC shops" are not "competent" for this car, and will just screw it up, probably with a compressor failure coming a year or two later.

    Any suggestions for a competent Prius AC repair shop (or mobile repair guy, I guess) in the Los Angeles area? Preferably in or close to the San Gabriel valley. Yes, Lech is in the same state, but unfortunately 400 miles away.
     
    #6 pasadena_commut, Sep 15, 2022
  7. ChapmanF

    ChapmanF Senior Member

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    I'm not sure "techstream limitations" is quite right ... if a Gen 2 has no refrigerant pressure sensor, for example, it's not Techstream's fault it can't show you the refrigerant pressure.
     
    #7 ChapmanF, Sep 15, 2022
  8. pasadena_commut

    pasadena_commut Senior Member

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    Agreed. If the Gen 2 had the sensors Techstream would almost certainly be able to read and display them.

    On a somewhat related note...

    The Gen 2 does have a refrigerant level sensor which prevents the compressor from running. In theory no compressor should ever run when there isn't enough refrigerant in the system to keep it healthy. Yet compressors do blow up. Why? Is it because contaminants let into the system by either incompetent technicians or through leak points destroy the compressors while enough refrigerant is present to pass the sensor test? If that was the case I suppose hypothetically one could splice in water and air detection sensors and piggy back that logic onto the existing pressure logic wire, so that the system wouldn't run for: too little refrigerant OR water present OR air present. I don't know anything about these two types of sensors, perhaps they cannot be run continuously, are big, or are very expensive.
     
    #8 pasadena_commut, Sep 16, 2022
  9. ChapmanF

    ChapmanF Senior Member

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    There isn't any refrigerant level sensor. What Gen 2 has is a dual pressure switch, which will open the circuit if the pressure goes unreasonably low or unreasonably high.

    But "enough refrigerant in the system to keep it healthy" is not a question that any pressure switch can answer. Why?

    Because as long as there is any amount of liquid refrigerant at all, the pressure when the system is off will simply be whatever the saturation pressure/temperature table for R134a shows for the current temperature. That will be the same pressure from well above the right amount of refrigerant, down to exactly the right amount, down to way below the right amount.

    The pressure will not drop further, below that saturation point, until there is so little refrigerant left that none of it is liquid. Then, eventually, the pressure can get low enough to trip the pressure switch.

    But damage can be done well before that.
     
    #9 ChapmanF, Sep 16, 2022
  10. pasadena_commut

    pasadena_commut Senior Member

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    Ah, got it. The existing pressure switch says "your compressor is probably toast" but the absence of a signal does not indicate that "your compressor is not in danger". That's roughly as useful as regularly seeing a cardiologist whose only medical skill is diagnosing massive heart attacks.
     
    #10 pasadena_commut, Sep 16, 2022
  11. ChapmanF

    ChapmanF Senior Member

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    What's more impressive is the very recent ones, where there reportedly are enough sensors and enough computational power in the ECU to actually make the judgment about correctness of the refrigerant charge and report that.
     
    #11 ChapmanF, Sep 16, 2022
  12. Adrien

    Adrien New Member

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    I have the compressor speed going up to 6500rpm for a Low setting and I have the engine radiator fan running constantly either on Low or intermittently at 20 degrees celsius. What does it come from ?
     
    #12 Adrien, Jul 19, 2023
    Last edited by a moderator: Jul 19, 2023
  13. mr_guy_mann

    mr_guy_mann Senior Member

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    I can't say anything about the compressor RPM without see what system pressures are on a gauge set and what the temperatures are.

    The radiator fan operation is normal for the A/C being on.
    Screenshot_20230719-124727.jpeg

    Posted via the PriusChat mobile app.
     
    #13 mr_guy_mann, Jul 19, 2023
  14. lech auto air conditionin

    lech auto air conditionin Senior Member

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    Prius easily reach 39°F to 43°F on 105° day Fahrenheit day no problem at all but only if it’s properly recharged.

    If you’re just one or 2 ounces off from the spec plus or minus it will not perform correctly.
     
    #14 lech auto air conditionin, Jul 19, 2023
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