Heater not working except far left vent

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by fiz, Dec 15, 2025 at 7:57 AM.

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  1. fiz

    fiz Junior Member

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    Vehicle:
    2011 Prius
    Model:
    Three
    Hi all, I’m experiencing a cabin heating issue on my 2011 Prius Gen 3 (UK RHD, London). Here’s a summary:

    • Symptom:
      • Cold air from most vents
      • Mildly warm air from left vent only
      • Fan works fine
      • Engine heats normally
    • What I’ve checked / considered:
      • Coolant level normal, no leaks
      • Left vent has mild hot air, so heater core is likely okay
      • One garage suggested regassing A/C (most probably irrelevant)
      • Another suggested heater matrix replacement (£450+, 4–5 hr job) — maybe unnecessary
    • What I suspect (also based in online searches):
      • Air-mix / temperature blend actuator failure (air-mix servo)
    • Part info:
      • OEM part numbers suggested online: 87106‑47030 (latest), 87106‑47020 (older compatible)
    • Questions:
      1. Can anyone confirm this is almost certainly the air-mix actuator?
      2. Anyone had this type of issue?
      3. Approximate cost if done independently?
    Thanks in advance for any guidance!
     
    #1 fiz, Dec 15, 2025 at 7:57 AM
  2. Tombukt2

    Tombukt2 Senior Member

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    So your hose is on the firewall going to your heater core one goes in one comes out they're hot as fire all the time forever except at start in am etc . You know this . Then it's that lil motor actuator . Crack it open you'll see all the nonsense.
     
    #2 Tombukt2, Dec 15, 2025 at 8:09 AM
  3. ASRDogman

    ASRDogman Senior Member

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    The A/C will NOT effect the HEAT! You should stay away from that guy!
    It's likely a vent that the arm has broken, or the servo.



     
    #3 ASRDogman, Dec 15, 2025 at 9:42 AM
  4. ChapmanF

    ChapmanF Senior Member

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    In a gen 3, I think I could confirm it's almost certainly not that. I think some trims of gen 4 maybe allowed driver and passenger to set different temperatures, and had two air-mix doors, but gen 3 has just one air-mix door for both sides, which couldn't easily cause the symptoms you've described.

    It might rather be that some of the passages of the heater core are clogged.
     
    #4 ChapmanF, Dec 15, 2025 at 9:44 AM
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