Auto A/C Has Stopped Working Automatically

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by bresna, Aug 31, 2020.

  1. bresna

    bresna Active Member

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    I don't know what happened. For some reason, my A/C keeps shutting off no matter what automatic temperature setting I set the car to. I can set it to max A/C and it still won't turn it on and the air coming out of my vents is hot. I suppose it could be the 12V battery was running low while I was on vacation for 10 days, but the car started with no problems.

    I checked the Auto A/C setting and it's set to "On", so it's not that.

    Any thoughts on this?
     
  2. Bob Comer

    Bob Comer Active Member

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    A leak in the A/C system is my guess. You need to take it in to get service.
     
  3. m8547

    m8547 Senior Member

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  4. bresna

    bresna Active Member

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    But when I press the A/C button and turn it on, the air blows cold as ever. If the A/C was leaking, it wouldn't get cold.
     
  5. Bob Comer

    Bob Comer Active Member

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    I didn't get that from what you said, but it still sounds like an A/C system problem.
     
  6. schja01

    schja01 One of very few in Chicagoland

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    Yea, the OP specifically said it blows hot air.:(
     
  7. bresna

    bresna Active Member

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    Thanks for this. I was unaware of this issue. Luckily (?) my fans appear to have been reconnected after my recall service so that doesn't appear to be my problem.
     
  8. bresna

    bresna Active Member

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    There was a hot day a few weeks ago and as I was driving down the highway in hybrid mode, I noticed that the car wasn't getting cool, no matter how low I set the automatic temperature to. I clicked onto the climate screen and saw that the A/C light wasn't lit. I pressed the button, it turned on the A/C and the car cooled down. I figured I somehow shut it off for some reason.

    The next day, I got into the car and as i was driving, in EV mode this time, I noticed that the A/C button was once again Off. I clicked it on again and thought, hmmm.

    After searching these forums, I found mention of the Auto A/C setting. I went and found that screen and I was disappointed when I found it set to "On".

    So now I'm asking if anyone else has had their A/C randomly turn off and refuse to turn back on, no matter how low you set the temp.
     
  9. Salamander_King

    Salamander_King Senior Member

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    So, what you are saying is that A/C is working fine, but the whatever controls the Automatic switching of A/C is not working and always defaulting to A/C off position?

    Have you tried without Auto? If you just use manual setting does the A/C switch stays on?
     
  10. bresna

    bresna Active Member

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    So this gets weirder... I notice that 100% of the time when I start the car, it comes up with the A/C button unlit, even if the Auto button is lit and the A/C should be cranking, like the other day when it was >90 outside. The fan was blowing hot air out of the vents.

    So I just have to click "Auto" and the A/C pops back on. I drive for a bit... maybe 15 minutes... and the A/C light goes off *but* the A/C still blows cold air. Huh?

    I have tried switch on & off the ECO drive mode. I have tried switching on and off the ECO Heat/Cool button. I have tried turning off/on the Auto A/C mode. None of these things change the functionality.

    I also tried going full manual mode. At first, it works perfectly. But again, after about 15 minutes, it shuts off the A/C and when this happens, unlike when it's in Auto mode, it starts blowing warm air.

    Is there some kind of protection circuit kicking in? If that is the case, I don't get why a simple button push turns it back on for another 15 minutes. If it were overheating the heat pump, I would think turning the A/C back on would result in it shutting right back off.

    I will probably bring it in for a dealer visit.

    FWIW, I have ~93,000 miles on it now if that helps.
     
    #10 bresna, Sep 10, 2020
    Last edited: Sep 10, 2020
  11. jerrymildred

    jerrymildred Senior Member

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    Whatever it is, it doesn't seem to be a setting. Looks like there's some sort of a malfunction. I agree that you unfortunately will need a dealer or another hybrid AC specialist to chase it down.
     
  12. m8547

    m8547 Senior Member

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    I wonder if it would work to reset the climate control ECU? Would it be as simple as disconnecting the negative terminal of the battery for a while?

    Or, in most Toyotas the climate control ECU can store error codes. The dealer should be able to read those with a techstream tool.
     
  13. RRxing

    RRxing Senior Member

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    It's worth a shot...
     
  14. ChapmanF

    ChapmanF Senior Member

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    On most Prius generations, the climate control ECU will give you trouble codes without any fancy scan tool, if you ask.

    I just don't know the details how to ask a Gen 4.

    Gen 2 and Gen 3, you'd just hold down the AUTO and the FRESH/RECIRC buttons while powering the car on.
     
  15. Elektroingenieur

    Elektroingenieur Senior Member

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    This still works on fourth-generation Prius and Prius Prime cars.

    On later models, if the air conditioning controls are part of the navigation system, turn the car on to ACC mode first, so the display works, and then hold the AUTO and recirculation/fresh buttons while changing to IG-ON mode.
     
    jerrymildred likes this.
  16. bresna

    bresna Active Member

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    I tried this and there doesn't seem to be a response.

    I did disconnect the negative battery terminal for about 20 minutes. I'll see if it fixes the problem. Otherwise, it's off the dealer.

    FWIW, yesterday I tried turning off Auto A/C control in the car settings and even doing that, it still shut off the A/C after about 10 minutes but strangely, when I turned it back on, it stayed on for the rest of commute home (about 40 minutes).
     
  17. RRxing

    RRxing Senior Member

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    So many of us feel this way... :LOL:
     
  18. Elektroingenieur

    Elektroingenieur Senior Member

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    Maybe it’s edge-triggered, rather than level-triggered: try changing to IG-ON mode, and then, within five seconds, press and release the AUTO and recirculation/fresh buttons together.
     
  19. bresna

    bresna Active Member

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    This worked and it appears that this may have solved my problem. I'll see after tomorrow.
     
  20. bresna

    bresna Active Member

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    Yesterday, it started shutting off again. So the reset seems to have fixed it for about a week. It was warm today so i had to drive home with the climate screen up on the display so I could hit the "Auto" button every time the AC light went off.
     
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