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AC and Heater only work intermittently

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by MFrancis, Apr 4, 2018.

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  1. MFrancis

    MFrancis Junior Member

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    Hi everyone,

    I have a 2012 Prius III with 110k miles, new 12v battery.

    I'm having an issue where the AC and the heater work intermittently. I'll have the AC on and it'll work fine for a few days, then stop for a few. Or sometimes it won't work when I start the car, and then randomly it'll start working 20 minutes later.

    The AC still cools very well when it's working, the heater works well when it's working. It just randomly gives up at times, only to come back on a day later.

    It had some front-end/wiring damage years ago, I'm assuming it's related to that, but wondering if you guys had any advice, couldn't find anything in other threads.

    The sound system is also dead (again), had it replaced before around 70k since it was under extended warranty, if that helps.

    Zero issues otherwise! Hoping to get another 110k out of my Prius.
     
    #1 MFrancis, Apr 4, 2018
  2. qdllc

    qdllc Senior Member

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    Well, to start, I normally have A/C stuff done by a professional, but...

    Are you in ECO mode when this happens?

    Are you driving towards the sun when this happens.

    I don’t have any insight other than I’ve found that driving towards the sun makes me feel hotter than it is, and I’d have to lower the temperature setting for the system to compensate. I also find that if it’s more than just me in the car, it feels warmer than it should...my guess being that ECO mode doesn’t let the system work hard enough to compensate for the extra heat generation.

    If indeed your A/C is in working order, maybe there’s a fault in the sensor that tell it what the cabin temp is. It blows cold at first then warms thinking it’s at the desired temperature. Alternatively, sine the compressor is driven electrically, maybe that’s cutting out ?

    I’m betting it’s an electrical issue affecting the compressor operation.
     
    #2 qdllc, Apr 5, 2018
  3. bisco

    bisco cookie crumbler

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    agree that is probably in the repaired wires. have someone trace them carefully for a short or chafing.

    since the heater does not work from the compressor, it is likely an electrical control issue affecting the hvac settings controls.
     
    #3 bisco, Apr 5, 2018
  4. ChapmanF

    ChapmanF Senior Member

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    Ever been any water in the cabin?
     
    #4 ChapmanF, Apr 5, 2018
  5. MFrancis

    MFrancis Junior Member

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    Thanks for the info guys. I only drive in PWR mode. The AC and heater either work perfectly, or don't work at all. No water in the cabin...so far.
     
    #5 MFrancis, Apr 6, 2018
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