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Intresting Problem, A/C only blows Cold Air when Engine is off in Electric Mode

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by Manny koutalides, May 17, 2020.

  1. Manny koutalides

    Manny koutalides Junior Member

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    2012 Prius C
    AS soon as the Engine kicks on, it turns hot as if im on the highest heat setting.
    A little background, MY A/C problems started when i wasent able to get the air to come out of the windshield vents (basically no front windshield defrost) I tried all the trick found on the forums and even replaced the a/c amplfier(used), still couldnt get it to come out of the windshield.

    I pulled off my glove compartment and noticed a few problems, im not longer able to used the re-circulate or outside air option. its stuck in the cabin air mode, I also can see the actuator atttached to the Evaporator Assmebly doesnt move when i cahnge from cold to hot, I am able to change from dash vents to floor, still on windshield vents.

    Somehow i was able to pull off the blend door actuator that attaches to the Evacuator assembly, but i noticed if i tried to manually turn the knob (with a long flat head screw driver) it was connected to, the knob turns freely, around and around as if its broken inside.

    I guess what im trying to figure out is if inside the Evac assmebly, could it be stuck in position thats drawing heat from the motor, im not keen on how the HVAC system in a car works and as you guys know, the cost to replace a Evacuator assembly is cost to $2k just for the part and th elabor is very extensive as hey would have to pull apart the dash and evac the refregirent

    i check out the fuses, they were good, is there a control switch that might have gone bad, my refrig levels are good,

    im lost, its my comuter car, from home to my Fire house in NYC 65 miles. and it could get pretty hot in the dead of summer in NYC traffic.

    hope someone can help. as shot around ideas or even educate me on how the A/C sytem goes from cold to hot in the car
    all the best
    thanks
    Manny
     
    #1 Manny koutalides, May 17, 2020
    Sonic_TH likes this.
  2. ChapmanF

    ChapmanF Senior Member

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    From your observations, it does sound as if one of the doors in there has somehow broken.

    The engine coolant is always piped through the heater core in there, so that is hot whenever the engine is running. The only thing controlling how much heat you get is the blend door, sending the air around the hot core or through it.

    If you're spinning the shaft for that door, and the engine is running, and it makes no difference in the heat you feel, the door must be broken off inside.

    Maybe pick up a used assembly for $100? Find what's broken, fix that, end up with a lot of spare parts?

    There will, I'm afraid, be no royal road to taking the dash apart.
     
    #2 ChapmanF, May 17, 2020
  3. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I think @ChapmanF has correctly called it; I agree with his theory that the blend door is stuck or broken. There isn't really any band-aid; somebody has to pull the dash apart and replace it. It won't cost as much as an evaporator replacement but it's still non-trivial.
     
    #3 Leadfoot J. McCoalroller, May 17, 2020
  4. Manny koutalides

    Manny koutalides Junior Member

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    Thank you Chapman and Leadfoot,

    quick questions, so the blend door is actually inside the Evap heater assembly and can be replaced without replcing the entire assembly?
    which like you guys said, would require the dash to be removed??

    more or less bassed on my problem and the fact that it blows cold when in electrical mode?motor off and when the car is cold, my car is basically producing cold air and hot air at the same time? its not like when the engine kicks on, its turning off the cold air?

    thanks for you help, really appreciate it
    Manny
     
    #4 Manny koutalides, May 17, 2020
  5. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    When the car is in ready mode, the AC is allowed to run which will cool the car.

    If the gas engine is running, and has been running more than a few minutes, then the car is also producing heat. You can't prevent this. The car normally ignores the hot air from the heater core by moving the blend door to accept only air from the AC evaporator. If the blend door can't be put in the correct position, then you will get some mix of chilled and heated air, and guess what- the heating system can overpower the AC just because it can.

    I don't think they have to change the evaporator unit, just the blend door motor and possibly the door itself.
     
    #5 Leadfoot J. McCoalroller, May 17, 2020
  6. ChapmanF

    ChapmanF Senior Member

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    As far as I know, the doors aren't sold separately. A dealer would replace the whole unit, at its whole magnificent price.

    But if you pick up a used whole unit for $100, you can play with how to take it apart and maybe get the door out of it, repair the one in your car, and have most-of-a-whole-unit worth of spare parts. Not bad for a hundred bucks.

    Or, after taking the dash apart as you'll have to anyway, you might just swap entire units, and again end up with most-of-a-whole-unit worth of spare parts.

    To fully remove the unit in the car, though, you have to have the refrigerant reclaimed, and then have the A/C evacuated and charged when you are done.

    If you can work out a way (by playing with the used unit on the comfort of your workbench) to get at a blend door without having to open the refrigerant connections, you can avoid that extra hassle and expense.
     
    #6 ChapmanF, May 17, 2020
    Leadfoot J. McCoalroller likes this.
  7. Manny koutalides

    Manny koutalides Junior Member

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    Thank you for the info... I think I’m going to take your advice and buy the part (thank you for the link) and see if it can be removed.

    if I do go ahead and try and replace it, I will try and do video or pics to show the removal of the dash and post it, unless I couldn’t find it, I’m not sure there’s one available online.

    what repair manual or subscription service do you recommend, that would give me the best step by step breakdown for removing the dash?

    I again thank you for your help, as much as these cars are really tough to work on, there pretty amazing, I find it fascinating how each system is incorporated into each other. My Prius C has been really good to me,
    Thanks Manny
     
    #7 Manny koutalides, May 17, 2020
  8. ChapmanF

    ChapmanF Senior Member

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    Elektroingenieur put together this wiki page with a pretty complete breakdown of your options.
     
    #8 ChapmanF, May 17, 2020
  9. Sonic_TH

    Sonic_TH Active Member

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    Same happens to my 2012 Prius C, except that it get's fixed when i disconnect the 12 V battery for a few minutes, but if i turn it to blow hot air and then cold again, the problems comes back.
     
    #9 Sonic_TH, Jun 27, 2020
  10. HiC

    HiC Junior Member

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    You can temporarily bypass the heater core by disconnecting the hoses at the firewall behind the engine and splice them together.
     
    #10 HiC, Jun 27, 2020
    Sonic_TH likes this.
  11. Sonic_TH

    Sonic_TH Active Member

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    Do you have pictures or diagrams on how to do that?
     
    #11 Sonic_TH, Jun 28, 2020
  12. lech auto air conditionin

    lech auto air conditionin Senior Member

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    I don't like dash removal. If it was my car. I would put in a electric heater control valve inline of the coolant hose to the heater core. Hit a button or switch no heat. hit the button again got heat.
     
    #12 lech auto air conditionin, Jul 2, 2020
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