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Toyota Sienna Heating / Cooling



  • We have the same problem in our '06 Sienna. We brought it to the dealership, but they couldn't figure out what was wrong - we should have checked this forum first. How do you remove the HTR relay? If you just pull hard enough, will the relay pop off? Do you need to pry the relay off with a tool? Do you remove the blue cover? Thanks.
  • khardingkharding Posts: 5
    To remove the HTR relay, you open up the fuse box under the hood near the driver's side, pop off the fuse box cover and then find the appropriate relay. On my '05, the schematic is on the under side of the fuse box cover. You should just pull the relay straight out like a fuse. I would avoid using a tool if at all possible so as not to break anything unless there is a special relay puller tool. The relay is in there tight, but with minimal wiggling, it should pop straight out. These relays cost about $18-20. I just switched out the RR A/C with the HTR relay and now we are dealing with the intermittent issue in the rear air. I will pick up another when convenient, but at least I know that this was the problem. I do not think the blue cover on the relay itself is removable. Good luck
  • xavyxavy Posts: 2
    Just purchased used 05 Sienna (50K) two months ago, wife noticed odorless vapor/smoke blowing out of center dash vent today. Has anyone ever encounter this before? What is the cause? Dealer wants us to bring in because they say they have never seen or heard of this issue.
    Are they just blowing smoke?
  • xavyxavy Posts: 2
    I purchased an OEM key today, and had locksmith cut key, no problem.
    Went to program myself, followed instruction, did not work. Any suggestions other than paying dealer $89.00 an hour for a 2 min. job? Thieves is the common word for them.
  • wwestwwest Posts: 10,706

    Humid day, A/C cools the air to dewpoint, you get FOG flowing out of the vents. Usually only lasts until the A/C is able to fully cool the evaporator down.
  • marty08marty08 Posts: 3
    I bought the Sienna in the Fall and when Winter came, we noticed that it takes over 20 minutes to get any considerable heat from the vents. If you let the vehicle in "Park", warming it up, it takes over 25 minutes to get any heat. When you drive it, within a minute of start-up, it is usually 20 minutes or 7 miles, before you get any heat. I've taken it into the dealership, under warranty and they stick the radiator and say it's OK. I tried to make them keep it overnight and start it in the morning, when it's cold and they claim that if it's at the correct operating temperature when they check it, it won't make a difference. I tried to explain that perhaps the thermostat is not closing all the way and the dealership stated that they have never heard of this. Has anyone else had this problem? I have a 97 4-Runner and a 90 Toyota Pick-up and both warm up within a few minutes and even the temperature guage goes to normal, just warming it up without driving it. :confuse:
  • wwestwwest Posts: 10,706
    Does the engine coolant temperature guage come up to the correct level in the normal time and yet there is no heat..??

    Or does the engine coolant not come up to temperature..??
  • mfc3mfc3 Posts: 8
    I have 2005 Sienna with only 10K miles. Now I press AC on/off switch and nothing happens. The AC switch light is always off. The air blows do work but they are just sucking air from outside. Does anyone know what is going on ? Where should I look for ? The car warranty just expired.
  • I had a similar issue with the switch in the on position, no A/C light, and no fan was functioning. I switched out the A/C relay in the fuse box and that seemed to fix it. I have not dealt with a fan that is working but A/C not working. Sorry.
  • mfc3mfc3 Posts: 8
    Thanks, kharding. I will go back to check if the fan is actually working. I did recall the rear AC fan is woring. Do they(rear and front AC) share the same relay ?
  • 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.
  • 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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