Prius Prime heat turns off after automatic car wash?

Discussion in 'Prime Main Forum (2017-Current)' started by P.Neophyte, Mar 11, 2022.

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  1. P.Neophyte

    P.Neophyte Junior Member

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    Last weekend in full EV mode and 23ºF outside and cabin temp set to 72ºF on Auto Climate, I drove 5 miles to an automatic car wash that pulled the vehicle through the wash as high pressure hot water, brushes, and dryers cleaned the vehicle. I brought the Prime there many times before, but maybe not when the outdoor temp. was that cold.
    When I exited the car wash, the A/C vents were blowing cold air and continued this for 15 minutes until I stopped and turned off the vehicle. When I restarted an hour later, the climate control returned to normal. Has this happened to anyone before? I suspect that the hot water and air may have changed the external thermostat (if there is one). It became uncomfortably cold in the cabin. Any thoughts?
     
    #1 P.Neophyte, Mar 11, 2022
  2. sam spade 2

    sam spade 2 Senior Member

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    I suspect that is what happened too. Yes there is an external temp. sensor.

    I wonder why you did not adjust the climate controls BEFORE it got uncomfortably cold ?
    :)
     
    #2 sam spade 2, Mar 11, 2022
  3. Salamander_King

    Salamander_King Senior Member

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    External sensor theory seems to be the answer.

    But did you have the car in READY and gear in "N" and running AC while the car was going through the wash? If so, it may be possible that you might have drained the 12v and or traction battery to the low point which the car sensed it and turned off the heat pump to protect it from draining further? I have never had that problem, but I don't use a drive-thru car wash that often. I havened used it for several years, but I am sure I have used it in very low temp down to a single digit. I can't remember for sure, but I think I had the heat and lights all turned off while going thru.
     
    #3 Salamander_King, Mar 11, 2022
  4. P.Neophyte

    P.Neophyte Junior Member

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    Well, I had it set to AUTO 72º, so I did not feel compelled to make any changes initially, but I did bump up to 78º with no discernible change.
     
    #4 P.Neophyte, Mar 11, 2022
  5. P.Neophyte

    P.Neophyte Junior Member

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    I did have it in Ready and Neutral and AC but there was plenty of charge in the traction battery. I assume that the 12v is still robust. I only have 13K on the clock, and it was only in neutral about the 2 minutes it takes to go through the wash.
     
    #5 P.Neophyte, Mar 11, 2022
  6. Trollbait

    Trollbait It's a D&D thing

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    The outside coils of the heat pump are really cold when heating the cabin. The wash water is probably just warm enough to not ice up the inside of the wash. That coil probably froze up, and the HVAC system was running in cooling mode to defrost the coil.
     
    #6 Trollbait, Mar 11, 2022
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  7. P.Neophyte

    P.Neophyte Junior Member

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    That is a fantastic explanation! It makes sense; however, it begs the question why doesn't the coil freeze when you are driving through splash water? I do not know where the coil is located. Maybe it is largely protected, or at sub 0ºC, we have ice, snow, or slush which may not be able to penetrate to the coil location.
    I really like this explanation! What do others think?
     
    #7 P.Neophyte, Mar 12, 2022
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  8. Trollbait

    Trollbait It's a D&D thing

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    The A/C condenser coil is in the front, before the radiator, where there is plenty of airflow to cool it. I once tried a 100% grill block, and the A/C stopped cooling when the car was stopped. A heat pump heating doesn't need to cool that coil, but it does need airflow to help in gathering heat out of the cold air.

    For aerodynamics, and to funnel air flow through the radiator, the front bumper assembly has a cover at the bottom. With closed grill shutters, not much water will get onto the coil. There will be regular defrost cycles, but quick enough that they can be unnoticed. A car wash means more water contact. The times that could be seen on the road is when the car is moving, and airflow can help remove any moisture before it freezes to the coil.

    Then the colder the outside temperature is, then the harder the heat pump is working to heat, and the colder the outside coil gets.
     
    #8 Trollbait, Mar 12, 2022
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  9. sam spade 2

    sam spade 2 Senior Member

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    SO.......if you wanted heat, why was the AC ON ??
     
    #9 sam spade 2, Mar 12, 2022
  10. sam spade 2

    sam spade 2 Senior Member

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    Like it or not, I think the first, simplest and most obvious guess probably is the right one.
     
    #10 sam spade 2, Mar 12, 2022
  11. Salamander_King

    Salamander_King Senior Member

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    "AC" on PP means HVAC for both heating and cooling. The car uses a heat pump for both.
     
    #11 Salamander_King, Mar 12, 2022
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