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My 2004 Sienna has developed a problem with the heating system.

hockingzighockingzig Member Posts: 4
edited October 2015 in Toyota
When I turn on the heat, I only get hot air through the drivers side vent,the passenger side vent is very cold. I had it in to be worked on (at a Non-Toyota shop)and they tore it completely apart and could not diagnose the problem. It affects the entire system,meaning the air going to defrost is also hot on the drivers side and cold on the passenger side. Any ideas what the problem might be?

Best Answer


  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    It sounds like some actuator or blend door problem. Did this shop have the scanner necessary to pull trouble codes for the HVAC system?
  • hockingzighockingzig Member Posts: 4
    I don't know what equipment they have but they told me they checked the actuator and tore it down all the way to the vent and couldn't find the problem.
  • 93tracker5spd93tracker5spd North East Ohio USAMember Posts: 194
    Hello! It appears from what I have found, that your model has a separate computer module for the HVAC system, and it is possible this could be the cause of your problem. But as Mr_Shiftright has said, it is necessary to read the codes to determine the most likely cause. I have posted a web addresses below, check it out. Good luck!


    AC/Heater Control Module

    An AC/heater control module is a computer that controls and automates the operation of the heating, ventilation, and air conditioning systems (HVAC).

    Symptoms of Wear or Failure

    HVAC system might not heat or cool properly
    Air distribution from the HVAC may be incorrect

    Related Repair Advice

    Fault codes stored in the HVAC control module should be reviewed as part of any HVAC system diagnosis
    As with most computer controlled systems in modern vehicles, the climate control system may need occasional software updates to address various issues. A quality shop will check with the manufacturer to see if there are any Technical Service Bulletins (TSBs) related to the problems you're having and will upgrade the software when possible.
  • hockingzighockingzig Member Posts: 4
    I guess I will just take it in to the Toyota dealer and have it serviced.
  • hockingzighockingzig Member Posts: 4
    Toyota dealer says the air distribution box is cracked,$2400 to repair! A 2004 with 233,000 miles will not get repaired at that price!
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    Cracked, eh? Well if the dealer can SEE the crack, maybe you can patch it up, if what they mean is just a housing and not a moving part?

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