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Toyota Sienna Heating / Cooling



  • mfc3mfc3 Posts: 8
    I finally found out it is a bad AC HTR relay. Therefore I decided to find out what is wrong inside the relay. I removed the blue cover from the relay, located the coil and feed them with 12VDC, measured the resistance between two bigest pins. It was 1K-3K ohms, too high to allow AC to work. Later I cleaned the two relay contacts, adjusted the contact postion, and measured the resistance. The contact now has near 0 ohms. Put the relay back and the AC works without any problem. It saves me $20 without getting a new one.

    I think the relay was made with poor quality. Once a while it must be changed. Too bad for a Toyota quality.
  • cxucxu Posts: 2
    I have similar issues for 2005 Sienna model with very low mileage. I think this is the Toyota quality issue and we should complain and get free repair.
  • mfc3mfc3 Posts: 8
    I believe so. But for now, there are not much you can do.
    Once a while, you need to remove the relay for cleaning. It is like changing oil every 6K miles.
  • cxucxu Posts: 2
    Hi, MFC3

    How can I remove the HTR relay from the fusebox. I already located the fuse box and also identify the HTR relay box (it has grey color cover, not the blue color). How can I remove this relay out of fuse box. I try to pull it out. I can not.

  • mfc3mfc3 Posts: 8
    The HTR relay is holding very tight. You need to push or pull very hard to get it out.
    Try to remove other relays nearby to get easy acess to the HTR.
  • cpongcpong Posts: 1
    I have the exact same problem. Is it repairable? My dealership also told me that's how it suppose to work.
  • mfc3mfc3 Posts: 8
    It is repairable but you need to know hot to do it right. If you do not have any idea about electronics, you should buy a new relay instead.
  • jeffj2jeffj2 Posts: 1
    I had the same issue with my 2004 Sienna (and notice that it is flagged now in consumer reports for this model/year). After initial warmup, cold air comes out. Normal temp is set at 70. I have to push driver side to 74-76 to keep having warm air come out. Also, I have to lower rear temperature to 67, since that is pumping out in overdrive.

    I also took to dealer and could find no problems with the "heat". I will reference the solar sensor and climate control next time I go.

    Thanks for the tips.
  • Has anyone checked the temperature output of the AC comparing front to rear? My front will go to 37-40 degrees with the rear staying around 50 degrees. Checked with a digital probe or analog "stick" meter. Upon occasion the rear AC puts out heat only while the front is cooling properly. The heating occurs with the rear in max cold setting. Anyone ever have this problem. Heating is intermittent so dealer cannot find it. What are your temperature differentials? This is on a 2008 Sienna XLS. Thanks.
  • adiehl13adiehl13 Posts: 28
    We have a 2005 Sienna. Oh my lord- we had this vehicle in the shop at least 4 times to fix the air conditioner. We could get arctic temperatures in the front, but the kids would get heat. I stopped at the dealer several times on a Saturday afternoon and asked for someone to come out and document this (because they never experienced this when we had it in for service). Very Frustrating.
  • adiehl13 -- did you ever find out what was wrong with the AC? If it is working now what did the dealership do?
  • Did you ever find out what was causing the rear to heat while the front was cooling?
  • yatesjoyatesjo Posts: 186
    You do realize that the lower blowers are always warm and the upper blowers are cold right? If you have fan set on the floor level, it will just suck in hot outside air so try adjusting it to use the ceiling vents.
  • wwestwwest Posts: 10,706
    Rear A/C almost always recirculate inside air whereas the front can use fresh outside air.
  • Thanks for the comments, in my case the ceiling vents were putting out extremely hot air in the rear while the front vents were putting out cold air. So hot that it was very uncomfortable on my head. I understand that there is one AC system, one compressor and set of freon tubes, but it seemed like a vent door in the system was routing heat instead of AC to the ceiling vents. I further understand that heat is not supposed to come out of the ceiling vents, but believe me it was. Any specific knowledge of former experience of how the rear air works, as it relates to heating and cooling would be appreciated.
  • jimoxjimox Posts: 1
    I am having the same problem. After reading your message, I tried to see if I could do what you suggested. So far, I was able to open the fuse box under the hood, but I had difficult time to identify the relay (fuse?). According to the diagram in my owner's manual (2005 Sienna LE), HTR (50A) is #57 and RR A/C is #62 (40A). It seems to me that the fuses #56-#66 are in one piece under a transparent plastic cover, and I had no idea how to remove it (I did manage to remove that plastic cover though). I am wondering if I was looking at the right place? Could you please offer some details on what the HTR relay looks like and how to remove it? Thanks in advance.
  • ojnucciojnucci Posts: 3
    There is a marked difference between the driver side versus passenger side air. The passenger side blows as you would expect, but the driver only get slightly cooled air. Anyone have any experience with this? I suspect there must be a bad sensor on one side or the other, but if so how do I replace it? THank you!
  • Dear ojnucci,

    I had the same problem on my 2006 Sienna in June 2008. I discovered yesterday the problem came back.

  • wallycoxxwallycoxx Posts: 1
    i have a 2006 sienna also that the ac works on the passenger side but only blows hot air on the drivers side-any suggestions on what to replace without going to the dealer for 100.00 an hour---thanks
  • gedgoudaslgedgoudasl Posts: 21
    Problem is resolved. A temperature sensor was unplugged which caused the computer to read that the rear of the van was at 20 degrees. So it did what it was supposed to do and turned on heat in the rear, as hot as 100 degrees. It took 5 times for a technician to realize from the diagnostic printout that a 20 degree reading in the rear was a problem. The sensor became unplugged when the dealer installed the DVD system. Works like a charm now.
  • 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.
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