AC system flushing

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by ilya980, Jun 8, 2021.

  1. ilya980

    ilya980 Junior Member

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    There are a lot of threads on the forum relating to AC systems on a hybrid, but I can't find answers to my questions.
    I bought this car new and almost immediately had a problem with AC compressor. It started to rattle with acceleration. Took it to a dealer and the dealer replaced the compressor, flushed, and recharged the system under warranty. The dealer said there was water and other contamination in the compressor. It worked for 6 years, but now I have the same problem. The dealer said the compressor needs to be replaced. It was last Fall. The compressor was working. I did not use the car much since then. Now the compressor is not working and the pressure on the low side is 0. I see no air bubbles.
    I looked at the techinfo about how to replace refrigerant and compressor, but I could not find any info on how to flush the system. If the system is contaminated, is the only way to replace components? Or is there a chemical or other flush possible? Suppose I add pure H134a, find a leak with a halogen leak detector then fix the leak. I would need to open the system. How do I decontaminate it then? Pulling a vacuum will not pull the condensed moisture and other dirt out. What would a dealer do except pulling a vacuum when the system was opened? Also, if the system is flushed, how do I know the right amount of ND11 oil to add? The manual says how to estimate it when replacing the compressor, but says nothing about flushing the system.

    Thanks.
     
  2. rjdriver

    rjdriver Active Member

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    This video might be of interest. The guy's voice can be grating, but if you plan on keeping the car another 6 years, his information here could be of value.
     
  3. ChapmanF

    ChapmanF Senior Member

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    It depends on how contaminated and with what.

    The question comes up with some urgency in cases where the wrong oil has been used. (The compressor is high-voltage electric, and even small amounts of oil incompatible with its wire insulation can destroy it.) There is a somewhat high-end flush machine (HECAT H-1000) that some shops may have, that has been reported effective to avoid replacing any more of the system than the compressor itself, if the mistake is caught and flushed out quickly.

    A flush isn't usually essential after just ordinary incursion of atmospheric air and moisture while the system is open for repairs. A good vacuum pump, applied for a long enough time, takes care of that. The key is to pull a low enough vacuum and hold it long enough.

    The recent Toyota manuals aren't specific on the vacuum to pull, they just say "evacuate the system" and assume the tech has been trained what that means. The Gen 1 manual said to evacuate to 750 mmHg or better, and that might have been a misprint: 750 mmHg (counting down from atmospheric) is something like 10,000 microns (counting up from true vacuum), which is a lightweight vacuum for HVAC purposes. But even at that lightweight vacuum, your condensed water will boil out as long as the temperature is above 53 ℉.

    It is possible the manual meant to say 750 microns or better, which is much closer to the vacuum range HVAC techs will really apply. At that depth of vacuum, water will boil out even at food-freezer temperatures.

    Specialized and well-maintained HVAC vacuum pumps, hoses, and fittings are needed to reach that depth of vacuum.
     
  4. ilya980

    ilya980 Junior Member

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    Very interesting. Thanks. I like Scotty and his videos, but there is some controversy to it. He has a good point, but at the same time there are expensive high-end machines like HECAT that do exactly what Scotty says should not be done - flushing. I did not use wrong oil on purpose, but I recently used Arctic Freeze AF22 product. Yes, should have used just pure R134a, but it is too late now. The AF22 does not actually say it has PAG in it, and says it is approved for ALL R134a systems (Auto Air Conditioning Repair | Arctic Freeze® FAQs (rechargeac.com) (3-rd bullet)). It has no warning about hybrids either on the website (Arctic Freeze® | AF-22 R-134a Auto A/C Recharge Kit (rechargeac.com)) or in the Walmart.com listing (Arctic Freeze Ready-To-Use Arctic Freeze Kit (California Only) - Walmart.com - Walmart.com) where I bought it. I suspect the compressor is still alive, there is a refrigerant leak somewhere, and I have no refrigerant in the system.

    I thought about finding and fixing the leak, replacing the compressor oil (with ND11, of course), cleaning the condenser, and so I asked how I could flush the condenser. The HECAT uses hfc245fa, but it looks like it is not easy to get and I only saw it in 50lb cylinders. On another hand, there is a spray that has 95% of hfc245a and 5% of r134a...

    I don't know anyone around who would have a dedicated HECAT H-1000 for hybrids. The dealer is very expensive, unfortunately. A new compressor is $1600 (just the part) and they would not even allow me to buy it at another online dealer. I don't think the compressor is dead (at least yet), but even if so a refurbished one is ~$500 on ebay.

    The vacuum pump I have says 5 Pa maximum vacuum, which, I think, is about 38 microns.
     
  5. ChapmanF

    ChapmanF Senior Member

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    I wonder if, for an occasional user, a sensible budget strategy would be to spend a bit on a known good quality micron gauge, to be able to see what vacuum depth is really being achieved, and then take a chance on a more moderately priced vacuum pump, and see if it can meet the bar.
     
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