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Toyota Sienna Heating / Cooling



  • erin602erin602 Posts: 1
    Mine was doing the same thing. After extensive research on dual climate controlled vehicles, the NUMBER 1 cause was LOW REFRIGERENT. I went to Auto Zone and purchased an 18oz bottle with gauge--$26.99. Read the psi when the compressor kicks on- if low then add. Listen and you can hear the difference. My driver side air is so cold now!!!!! Yipee and I saved alot of time and money :)
  • ateixeiraateixeira Posts: 72,587
    Kudos for a nice DIY-fix.
  • lunarmistlunarmist Posts: 41
    We found a puddle of oil on the ground just behing the rear passenger tire. I assume it is from the rear AC unit. I checked and there is no cold air from the rear vents. The front AC is still giving out cold air. The local Toyota dealer said the front and rear AC units share the same R-134a refrigerant.Also, what should I notice looking through the little glass window on top of the receiver/drier? Does a can of R-134a also include the oil? Am I looking at a very expensive repair?
  • ateixeiraateixeira Posts: 72,587
    Where is whats-his-name? He would know.

    All I can recall is him saying the rear has an evaporator but not a seperate compressor.

    Are you sure it was oil? Usually I only get water from the condensation there.
  • lunarmistlunarmist Posts: 41
    So far so good, I added a 16 oz container of all-in-one refrigerant and oil to the system and I'm getting very cold A/C from both the front and rear. Still would like to know if the oil leak has been experienced by anyone else?
  • My 2000 Sienna AC worked fine for an 8 hour trip, next day no cold air. The AC push in switch lights up green, no flashing light to indicate an AC problem. My question is this, could I lose freon over night from a leak, and what types of problems would a flashing AC light be triggered by ie) no freon. In addition, how can I tell if my compressor is not engaging.
  • nic11nic11 Posts: 1
    I have a 2003 Sienna. Last weekend, the ventilation system made some strange sounds for a few minutes. After that when I drive fast enough I can feel the flow of air from outside coming in although the fan control is in the off position. I took it to the mechanic and he thinks that this is the normal the ventilation operates. But I don't remember the car letting the airflow in when the fan control was in off in the past. Can anybody please let me know if that's how it's supposed to be or not?
  • wwestwwest Posts: 10,706
    If you put the system in defrost/defog/demist mode the natural airflow due to forward speed will be minimized. I would recommend recirculate mode but some modern day systems will automatically switch back into fresh mode within ~2 minutes if the A/C is off.
  • Yes, This works. Thank you.
  • Hi mafaust, have you resolved this issue? I'm having the same issue with our 2008 sienna.
  • Hi guys,

    I am 2005 Toyota Sienna owner. I have very low mileage less than 10,000 mile on this van. This summer, I had the front fan die on me. The fan will not turn on. The rear fan works without problem. Since it was just over 3 years old, I did not want to pay for the cost of fixing the AC fan or Heater fan problem. Today Dec 22, 2009, I finally spend an hour trying to figure out the problem. Guess what? The stupid heater relay! Since it had two of the same relays, I switched the relay to see which one was defective, Guess what? The front fan will work now. The back will not.

    I looked at the part number; it is a Denso part, made in Tennessee.

    Who should I blame on the failure? This relay should not break. I am so disappointed, I am seriously will think twice next time when I purchase a new car next time.

    Knowing where it is made seems to matter a lot. I am buying a piece of garbage made in USA from Toyota!

    Toyota! you better get your act together, the next time it happen, you will have 1 less customer!
  • Since the AC or the Heater fan relay cause so many people problems. This is a defects in material workmanship and quality control issue in Toyota USA. Toyota is hiring idiots doing their testing and adjustment of the electro mechanical relay. They need to fire that person running the Denso parts plant in Tennessee.

    They need to do that SOON before the Toyota name and reputation go down the drain like you know what happen to GM and Chrysler.
  • ateixeiraateixeira Posts: 72,587
    It's still the most reliable van out there.

    Even if it is bad, it's less bad than any competitor.
  • I recently purchased a 2010 Sienna LE AWD. It has the manual climate control and interestingly enough, you cannot control the rear cabin temperature from the controls on the dash.

    You actually have to reach over your shoulder and make an adjustment on the temperature control located above the left sliding door!!

    My thought is, can I replace that controller with a digital controller from an XLE and it function correctly? Can I replace the one up front with a digital one as well?

    It comes down to if the Sienna's all use a common wiring harness with certain wires unused on the lower end models.

    Anyone with intimate knowledge of this system please chime in!

    Thank you.
  • My 2001 Sienna has 130k miles on it, and everything is fine. In past decades, common wisdom dictated changing water hoses every four years or so, and obviously, I've doubled that, and put a bunch of miles on to boot. I've had people tell me modern hose compounds make them last much longer, but I remain skeptical and am wondering if I should preemptively change them all out.

    Any Toyota techs have advice?
  • wwestwwest Posts: 10,706
    "...common wisdom dictated.."

    No doubt "common wisdom" widely dispersed mostly by dealer service personnel/managers....
  • crodycrody Posts: 6
    The van is 2007 Sienna CE bought new in 2007. Never see condensation water on the garage floor after using AC . I can always see a puddle of water under a 2005 Camry after using AC. By the way, the van's AC is not very cold.
    Can you see condensation water under your Sienna after using AC? Thanks.
  • Get a digital thermometer and check you AC temperature. Sitting still it should be in the 40's moving down the road will be about 40 degrees. Check on the dash vents. Likely you will find it 60 degrees or better. Low freon results in no condensation. With the numbers in hand your mechanic will have a better chance of solving your problem.
  • wwestwwest Posts: 10,706

    Only on max heating and low blower speed when reheat/remix plenum internal airflow path is not active.

    Most newer systems, certainly automatic climate controls, once the cabin is cooled to within a fairly narrow range of "setpoint", avoid discomforting the front passengers with outlet airflow that is TOO cold and dry.
  • Here in Minnesota having heat is a good thing. I noticed this weekend that when I am sitting and idling the heater in the front does not blow warm air. As soon as I start moving, the air temperature coming out of the vents gets nice and warm.

    This weekend I was sitting long enough that the engine temp guage climed well above the mid-point, (waiting for teenage daughter who was just going to be a "minute") so I know that the coolant was more than warm enough.

    I often have the controls set to recirculate and am not sure if the same problem occurs when not in recirculate mode.

    Since I get warm air once the van starts moving, I am assuming that the heater core isn't plugged and that the valve to the core must be open (or are those bad assumptions?)

    This is a 2005 Sienna with 113k miles. Electronic dual controls from heat/cooling.

    Any ideas?
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