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A C compressor causing P0AA6 code

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Seymour1, Jul 19, 2024 at 4:03 PM.

  1. Seymour1

    Seymour1 Junior Member

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    My newly purchased 2010 Prius with 229,000 miles has a blown 40 amp fuse for the A C compressor. And, I was getting P0AA6 codes, yellow triangle and "Check Hybrid System". I bought a Vici 500 volt megohmmeter. The battery is O K. The motor/generaters are O K. I disconnected the cable going to the A C compressor. The fused side of the cable acted like charging a capacitor to > 20 megohms. The unfused side read 0 ohms with the Vici tester. The inverter reads 1.9 megohms.
    I cleared the codes and did not reconnect the compressor cable. When I drove the car, there was no triangle or "Check Hybrid System".
    For the time being, I want to drive the car without buying a new compressor. The inverter has an empty hole where the cable was plugged in. I worry about dirt entering the inverter. If I plug in the compressor cable at the inverter, will the triangle or the "Check Hybrid System" cause a problem? Would it be safe to unplug the high voltage cable at the compressor? I do not plan on turning on the A C controls on the dash.
     
    #1 Seymour1, Jul 19, 2024 at 4:03 PM
  2. ChapmanF

    ChapmanF Senior Member

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    Wow! You mean this one, right?

    [​IMG]

    I would never have guessed that one would be 40 amps. That would be over 8 kilowatts at 201.6 volts, and I've never seen the A/C exceed 3 kW. I might have guessed the fuse was 15 or 20 amps. But it sure does say 40A in that picture, doesn't it?

    You could disconnect that cable at the compressor, and put a bunch of turns of self-fusing silicone tape (e.g. Rescue Tape) around the disconnected end to insulate it, and find a way to secure it from banging about, and then reattach the inverter end to keep that opening closed.

    This will either give you another P0AA6 or it will not. If it doesn't, you can go on driving until you feel like replacing the compressor. If it does, you'll know the fault is in the cable and maybe not the compressor, and that might be welcome news.
     

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    #2 ChapmanF, Jul 19, 2024 at 5:40 PM
  3. Seymour1

    Seymour1 Junior Member

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    Yes, I also did the math. That is a lot of power. Fuses are over-sized to eliminate nuisance fuse-blowing. They are mainly there to protect wiring or a stalled motor. And, the inrush surge current when the compressor starts is higher than when running.

    I am wondering if I also need to replace the dryer and condenser at the same time as the compressor. Some recommend doing that because of air entering the system when the hoses are unscrewed. But, even if I have a new dryer, condenser and compressor, at some point I must open the end of the hoses, compressor, dryer and condenser before attaching the parts together. And air will enter!
    If I can unscrew the hoses on the old compressor, mount the new compressor and re-attach the hoses very quickly, maybe I will only need to replace the compressor?
    I am confused by some youtubes. I saw where some oil remains in the hoses. And, if I add the proper amount of oil to the compressor, then, there will be too much oil. But, nobody knows how much oil is in the hoses.
     
    #3 Seymour1, Jul 19, 2024 at 6:23 PM
  4. Seymour1

    Seymour1 Junior Member

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    And the fuses cost $35 each.
     
    #4 Seymour1, Jul 19, 2024 at 6:24 PM
  5. ChapmanF

    ChapmanF Senior Member

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    As far as I know, that's always been part of the art-vs.-science aspect of this whole business. Sometimes, too, the new compressor comes with oil in it. I remember seeing references (not from Toyota that I've seen, just more general) that gave rules of thumb for how much of the new oil to pour out, based on which old parts of the system are being reused and assumed to have oil in them.

    Yeah, that always used to be the rationale when you had a big old utility motor that would just have a big contactor close at line voltage to start it. But this compressor is a motor with its very own variable-frequency drive built in that has control of voltage, frequency, phase, and current. I really doubt its startup behavior looks much like that at all.
     
    #5 ChapmanF, Jul 19, 2024 at 6:46 PM
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