Last post on Jul 25, 2013 at 4:08 AM
You are in the Toyota Sienna
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Toyota Sienna, Heating / Cooling, Van
#139 of 182 Sienna 2008 Rear Heat Issue
Dec 01, 2010 (5:54 am)
On my 2008 Sienna I setup the air to be hot in the front and I also setup to control the rear to be hot. While I am HOT in the front I found out there in only COLD air coming from the rear vents. My kids are freezing and there is no way they can tell me that is COLD because they are 6 months and 1 Ĺ . I took the car to the dealer at the moment it was happening and even though the guy saw that it was COLD air coming from the rear vents either way he tried , so at the end he told me to set up the AIR to come out from the floor vents , because the vents on the floor were giving HOT air , that way at least my kids wonít get COLD air from the rear VENTS , just while they found an appointment for my car, I had to come back after three days and what happened? They said everything looked fine! There was nothing wrong, that the rear vents are made to only give COLD air. What!!? And he also mentioned that the rear right vent is supposed to give warmer air. What?? I donít think they are right. I am waiting for this to happen again but I donít want to go thru this ONE MORE TIME! My kids donít deserve it! I paid for a NEW CAR to be working OK and so far this looks like a LEMON car because I reported this problem when my car had 300 miles (winter) , now that has 12000 miles (WINTER AGAIN) it is happening again. What do you recommend to do?
#140 of 182 Re: Sienna 2008 Rear Heat Issue [caro1216]
Dec 01, 2010 (9:25 am)
Regretably "They" are correct, your automatic climate conntrol system is operating AS DESIGNED.
NipponDenso/Denso US, actually has a US patent, "two-layer airflow", regarding this aspect of their HVAC designs. Under the patent warm air for heating is ONLY distributed through the floor vents while cooling airflow primarily through the upper vents. Being able to get HEAT from the front "cooling" vents is a compromise of the "two-layer" airflow aspect so the windshield can be heated in cold weather.
There are a couple of C-BEST options that can be an aid. Two of those allow you to disable the A/C compressor for an indefinite period simply by switching it off manually ONE TIME. Second one unlinks A/C from operating automatically in defrost/defog/demist mode. Yet a third option will prevent the system from automatically switching into cooling mode once the cabin atmosphere is raised to your temperature setpoint.
Otherwise you MUST be fully alert and quickly switch the FRONT system back into heating mode once it automatically switches into cooling mode.
In some climatic conditions leaving the A/C enabled will/might be an aid in keeping the windshield defogged or defogging it. But in other climates the use of the A/C will often result in sudden and spontaneous windshield fogging subsequent to the A/C use for defogging.
#141 of 182 Re: 2005 Toyota Sienna Mini Van Heat at idle question [ctbas2005]
Dec 18, 2010 (7:02 pm)
I am also having this exact problem. Can you let me know how you resolved it? Thanks so much.
#142 of 182 Re: Sienna 2008 Rear Heat Issue [wwest]
Dec 20, 2010 (6:04 am)
thanks for replying, but I have one more question. My car doesnt have the automatic climate control system. I have been able to bring the car two more times to the dealer and they have seen the two scenarios in my car. I had put the HOT air and also control the back fron the front panel and COLD air still coming oout fron the rear vents while in the front is HOT HOT HOT. Also, the second scenario, both, front and reas VETNS are HOT HOT HOT, so what is the problem here? They have tried to reproduce the problem with out success. Now, there is a problem if you say there is suppose to be COLD, so why there is HOT HOT air coming out?
#143 of 182 Re: Sienna 2008 Rear Heat Issue [caro1216]
Dec 22, 2010 (4:23 pm)
Carol, on the manual system the rear vents are set up so that upper = cold, lower = hot. I run into that on my own van where my kids will get cold if I forget to switch upper to lower when the weather changes.
As he said it is the designed function. The reasoning is simple: hot air rises, cold air falls so you get maximum mixing into cabin air if you put the hot flow low and cold flow high. Designing the heating coils to go low and cold coils to go high is also a lot simpler and cheaper than designing both to go both ways.
#144 of 182 Re: Sienna 2008 Rear Heat Issue [yatesjo]
Dec 31, 2010 (6:22 am)
Jan 03, 2011 (6:40 am)
Then this is strange. I had checked again the VAN and the rear vents were blowing hot iar between 74 to 84 degrees, and that was only the begining, after running the car for another half hour it reached almost 100. And that is the way it was at the beginifn, the first year I was always in the back of the car, so there is definitly sometihng worng with this car, it doesnt follow a pattern
#146 of 182 Re: '05 Sienna A/C quit working completely [jimox]
Jan 10, 2011 (10:57 pm)
I have the same problem with my Sienna 06. Looks like the whole panel of fuses for A/C, fan, heater, etc (#58-68) is missing. There is, however, a transparent fuse box. There is another fuse panel in the instrument panel, driver side, but I can't figure out how to access it. Do I have to remove the instrument panel to access the fuse box? Thank you very much for the information.
#147 of 182 How do I access the front blower motor?
Jan 21, 2011 (7:04 pm)
I'm pretty sure the front blower motor is bad. How hard is it to change out, and how do I access the blower motor?
#148 of 182 2006 Sienna XLE heater problems
Feb 03, 2011 (7:51 pm)
Having gone through this whole thread, I'm beginning to wonder of the climate control is behaving as designed.
The front vents are nicely blowing hot air as we go down the highway when suddenly, they start blowing cold air. To get warm air again, we have to jack up the temp settings extremely high which causes it to blow *very* hot air and we have to dial down the settings to their usual position. The cycle then repeats.
Somehow, we don't remember it behaving this way in previous winters but it may have.
The other and possibly related problem is that the air from the upper vents is not as warm at a given setting, say 72-deg, as our other cars. As per this thread, this might be as per design.
Don't even get me started on the fogging of the interior glass surfaces!
The dealer found nothing wrong the last couple of times.
Are there C_BEST (what the heck is that any way?) settings that might get the system the way we expect it to i.e. not be overly intelligent? I have a service visit coming up.