Going through carwash is causing issues climate control

Discussion in 'Gen 5 Prius Care, Maintenance and Troubleshooting' started by Rachael71, Jul 9, 2026 at 2:49 PM.

  1. Rachael71

    Rachael71 Member

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    So, this has happened to me a few times now. When I go through the car wash, my car emerges with wonky readings of the climate control system, lasts a few hours and then it rights itself.
    Yesterday, I went through car wash after work and the A/C stopped working. I did panic a little bit but then decided to just wait until morning, having experienced issue w/temperature readings before right after a wash.
    Sure enough, this morning it's working fine.
    Any one have any ideas or has had a similar issue? My car is going into the shop in a week for wheel bearing repair. Has 141k miles currently.

    Thanks everyone.
     
    #1 Rachael71, Jul 9, 2026 at 2:49 PM
  2. Rachael71

    Rachael71 Member

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    hmm, some quick googling seems to indicate the sensor is behind the front bumper and getting doused with water and causing things to be off for short period of time. Weird, that my mechanics had no idea about this possibility as I did talk to them about it.
     
    #2 Rachael71, Jul 9, 2026 at 2:55 PM
  3. rjparker

    rjparker Tu Humilde Sirviente

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    What wonky readings? Tried looking up "wonky readings" in the repair manual without success.
     
    #3 rjparker, Jul 9, 2026 at 3:17 PM
  4. Rachael71

    Rachael71 Member

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    Showing 30 degrees outside when it's closer to 50.
     
    #4 Rachael71, Jul 9, 2026 at 3:47 PM
  5. BiomedO1

    BiomedO1 Senior Member

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    Your posting in the gen5 forum. Are we discussing a gen5 or the gen3 in your profile?

    Are both radiator cooling fans turning when the AC is ON?
     
    #5 BiomedO1, Jul 9, 2026 at 4:01 PM
    Brian1954 likes this.
  6. rjparker

    rjparker Tu Humilde Sirviente

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    Its fairly normal for the ambient temperature sensor to drop 20f after a high pressure drive through car wash with foaming suds. The foam covers the sensor, causing it to take longer to read accurate air temperature because the sensor is affected by evaporative cooling.

    However most of us never use ac in 50f weather. Reading 30f, the car is trying to protect the ac from freezing.

    I think the only solution is to a) don't go the car wash unless its 60f or above, b) move the ambient sensor into the engine compartment which would result in high readings but the ac would work or c) create a shield to protect the sensor from the high pressure soapy water.
     
    #6 rjparker, Jul 9, 2026 at 4:32 PM
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