2010 Prius AC only turns on through defroster

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Riotmode, Aug 4, 2021.

  1. Riotmode

    Riotmode New Member

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    I've got a somewhat bizarre problem with my Prius. As stated in the header, the AC can only be enabled through the defroster! I can't get the auto mode to engage it, and the AC button is entirely unresponsive and refuses to even light up.

    Even weirder, the button DOES light up during the AC diagnostic, so the light isn't just burned out or something the button just isn't responding. The auto button does start the fans, but never the AC, which is curious since it's been consistently 80+ degrees out here every time I've tried it.

    Does anyone know what's going on or what to smack with a wrench to get it working again?
     
  2. burrito

    burrito Member

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    I'm not sure if it's industry standard, but I know at least some cars silently default to defrost mode every time you turn off your car. The idea is that if there's a failure, you'll at least be able to drive safely.

    If something happened to cause the louvers to get jammed into place (stuck in defrost mode), the fix might be as simple as finding and removing the jam/debris.

    Simple, but not easy.

    Of course, I could well be barking up the wrong tree, here. At least it's something to look into.
     
  3. Riotmode

    Riotmode New Member

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    This sounds like as good a starting point as any. Do have to ask though, what are louvers? Haven't seen the word before and googling it is defining it as those slats you sometimes see on skyscraper windows or the backs of cars
     
  4. burrito

    burrito Member

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    I don't know if that's what other people call it but I'm referring to the internal mechanism that changes which ducts the air is getting pushed through.
     
  5. rjparker

    rjparker Senior Member

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    Blend door actuators
     
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  6. ChapmanF

    ChapmanF Senior Member

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    Sounds to me like you've nailed it, the button. If it were mine I would pop the control panel out and see how hard it is to clean the contact surface behind that button. Toyota discourages that, but I've taken my chances before with good results.
     
  7. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I’m thinking your AC only works when you push the front defog button; is that right?
     
  8. Riotmode

    Riotmode New Member

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    sorry for the delay, yes that is my problem. I'm not sure how to pop open the buttons.
     
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  9. rjparker

    rjparker Senior Member

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    While the button theory sounds reasonable, the Auto mode should run the compressor as long as the temp is above the default 68f and a dealer has not intentionally turned off the feature. It drops out of Auto if you adjust the fan speed. I would assume your outside temperature is displaying accurately.
    8F2AFCBC-09AC-4FDE-B7D8-2B9D43CAD578.jpeg
     
  10. Noahdoge

    Noahdoge New Member

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    I would suggest to check your fuses to see if any of the ac ones are blown. If they are the Prius may be putting it into some kind of default safety mode or something.
     
  11. Riotmode

    Riotmode New Member

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    outside temperature seems to display right, but no it doesn't engage through auto in the first place. AC will ONLY engage through the defroster mode.
    I'll check fuses and make sure everything's in order, but I'd be surprised if it's a fuse problem since the buttons seem to respond except that they don't do what they should.

    It's... very weird and I don't know how to adequately describe the button situation.
     
  12. ChapmanF

    ChapmanF Senior Member

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    If the A/C will work in defog mode, and the A/C green light works during the self test, and you can't make the green light turn on and off by pressing the A/C button (while the blower is on), then the button is a suspect and there aren't many others.
     
  13. burrito

    burrito Member

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    But he can't just change modes either, right?

    Does the recirculate button work? What about the one on the steering wheel?
     
  14. ChapmanF

    ChapmanF Senior Member

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    I get it—we're reading the original post in completely different ways.

    Some of us are reading "the AC" as meaning "the whole HVAC system", and "the AC can only be enabled through the defroster" means the system can never be made to blow any direction but up.

    Others of us (me included) are reading "the AC" as meaning "the part of the system that refrigerates the air", and are reading the post as meaning that the blower, the heat, and all the outlet directions work fine, but it just doesn't refrigerate the air (except when defogging, because it's automatic then).

    So maybe the thread will seem less chaotic if the OP clarifies which reading was meant.
     
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  15. Riotmode

    Riotmode New Member

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    update: I've checked the relevant fuses, nothing pertaining to the AC or display panel is blown. The heck?
     
  16. Riotmode

    Riotmode New Member

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    The latter is correct here. The heater works just fine through any vent, but the only way to get the air cooling to engage is by activating the defroster. I can't switch modes afterwards without turning it off either, and no configuration of buttons I've tried has been able to get the cooling on through normal means. Not the steering wheel, not the auto mode, and definitely not the AC button.

    What's doubly odd is the auto button clearly works. I push it, the fans come on, even the heat if necessary, but NEVER the cooling. I'm thoroughly baffled.
     
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  17. ChapmanF

    ChapmanF Senior Member

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    If you can find a control panel from a recycler for a price you're willing to gamble, I would just pop out the one you've got and pop in the replacement and see what changes. If that makes a difference, you also then have the old one out, and may easily see how it can be further disassembled to spot the problem.

    If popping the old panel out and a replacement in takes you more than two minutes, it will only be because you're doing it the first time.

    I would lean toward trying a panel from a recycler because the new price is a bit salty.
     
  18. Riotmode

    Riotmode New Member

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    Unfortunately some recent events have left me pretty deep in the poverty hole, I doubt I'll be able to afford so much as a new oil filter for the next few months.
     
  19. Riotmode

    Riotmode New Member

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    Oh also I would like to note this doesn't seem to have the row of buttons that are the problem here, I do not know if that's the wrong model or if the picture is wrong or what
     
  20. ChapmanF

    ChapmanF Senior Member

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    Angle of the photo. The horizontal button-row runs across below the liquid-crystal display.

    If even a recycler unit is cost-prohibitive, you still have the $0 (possibly) option of taking out the control panel you've got, and inspecting it to see if you can disassemble it without damage and clean up some button contacts. If my hunch is right, this may work. However, the easy swap-with-another-unit gives you a quicker and less-risky way to find out if my hunch is right, before you try to disassemble the only control panel you have.

    It goes without saying that Toyota doesn't give any sub-assembly-level repair instructions for that panel; they only expect it to be replaced as a unit. That doesn't always mean it can't be disassembled or repaired, only that you're on your own to figure it out. If it gets damaged in disassembly or turns out hard to reassemble, then the cost isn't $0 anymore.

    But there are threads on here from appearance mavens who have taken theirs apart just to change the color of the backlight LEDs, so clearly it's not prohibitively hard.
     
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