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More likely than not your coolant is low, the engine is "threatening" to overheat and with the engine at idle no coolant flow gets to the heater core.
You should NEVER use recirculate at any time that A/C cooling is not required/used.
:confuse:">
But the human comfort equation relies on more than surrounding cabin air temperature. The lack of radiant heating from a COLD surrounding landscape, OUTSIDE surrounding landscape, can have a seriously adverse effect on your comfort level.
There are several C-best options that your dealer can set that might be of help. The system can be set such that you can disable the A/C for an indefinite period, throughout the winter period, for instance. Set both of these opposite the factory default.
A relatively new one is the ability to have the system remain in heating mode should outside climatic conditions dictate. Otherwise the system will automatically shift into COOLING mode, coolish and dry outlet airflow to your face, neck and upper body, once the cabin temperature as risen to a close range of your control setpoint.
Somewhat discomforting to say the least.
Yes another idiot design from our "friends" at NipponDenso, the company that has now brought us the UA episodes.
I have a 2010 Sienna XLE. Over the last couple days, the climate control setting have changed upon restarting the car. In one case, my wife turned on the car and the fan was blowing full blast. We never run the fan any higher than speed 1 or 2. On two other occasions, it changed from external air to internal air recirculation. In all 3 cases, these changes occurred after starting the car.
Someone suggested elsewhere that the automatic climate control system might set itself to bring the interior of the car to the previous temperature setting. However, in all 3 cases, the car had only been stopped for a short period - just long enough to pick up a kid at preschool. So there wasn't a tremendous change in interior temperature that would necessitate a sudden change in fan or air source settings. Also, this never happened during the summer, when the interior got really hot - the AC didn't automatically start going full tilt upon starting the car.
Because of the well-publicized recall of other Toyota models, and the revelation that the acceleration problems may not be entirely due to sticky accelerator pedals but possibly due to electrical or computer problems, I'm concerned that what I'm seeing is a symptom of a problem in my Sienna.
Has anyone had similar experiences, or any specific advice? I'm thinking about bringing it in for a service check.
Thanks,
LHM
In cold climates this situation, "stopped for short period" represents the greatest propensity for quickly fogging over the interior surface of the windshield shortly after restarting the car and driving away.
There are clear indications that Toyota/NipponDenso has begun to pay more attention to this issue as the 2010 systems will now automatically switch back into heating mode, or even heating/defrost/defog/demist combined mode should climatic conditions so dictate.
What you are seeing might be the result of NipponDenso's newfound focus on these problems.
These systems make use of the A/C system all year around, in the wintertime primarily for dehumidification of cabin airflow as a preventive measure against windshield fogging. The problem is that during that use lots of moisture is condensed onto the 10,000 square inches of evaporator vane surface area. As it happens much of it will remain there even overnight if some preventive measure isn't made/taken.
Read about the EED, Electronic Evaporator Dryer, at airsept.com for a good tutorial.
So the HIGH fan/blower speed upon re-entering/restarting the car may be Toyota/NipponDenso's answer to a long standing, VERY long standing (1990 and on...) problem with their automatic climate control systems.
I guess I'm sort of surprised that the rear windows aren't lowered ever so slightly at the same time the blower speed is raised. Actually, have you checked to see of the rear "winglet" windows aren't automatically opened slightly at the same time? If not that might be a practice you will want to take on manually.
Do you think this also might attribute to the same switch you found? I'd hate to have to pay toyota an arm and freakin leg to get this fixed if all I need is to replace a relay switch. What did you end up doing? Or did you just sell the lame thing?
-Lacey
The rear fan in my 05 Sienna stopped working completely. Niether hot not AC no way it does not budge. The front vents do work properly with Heater as well as AC. Not sure where to look. Possibly a relay or a fuse but no idea how to find. Any help would be appreciated.
Thanks
deep
Injected a dye but see no leak. Any other tips for troubleshooting?
Thank you.
So, is the compressor clutch cycling or continuously engaged..?
On my matrix, the aluminum pipes (with the H) goes cold and the CC cycles. On my sienna, it does not go cold at all. Is there a fuse for the compressor I can change or something? TIA
The only way I know to see "flow" in that sight glass is to have observed the transition from gas to bubbles to liquid as the compressor cycles on and then from liquid to bubbles to gas once the compressor cycles off.
If you are seeing flow then that is really good news as that would mean the refrigerant is going through the complete HVAC cycle. Evaporative cooling in the evaporator and then compression and heat removal in the condensor.
In that case you may have a heat/cooling reheat/remix control door/vane/damper stuck in the FULL HEAT mode.
my ac seems to be working in the rear ceiling vents, but the front is only blowing out hot air.
any ideas as to how this could be happening?
thx much
Hope this helps.
Sienna start-up procedure after setting in bright Tampa sunlight:
A) Open the rear quarter panel venting windows.
Turn the A/C on, the blower to maximum and the temperature control just a tad, one "click/notch", below maximum cooling.
C) disable recirculate mode.
Once the previously heated cabin atmosphere, HOT cabin atmosphere, is purged then close the rear vents and return the temperature setting to maximum cooling (the system will automatically go into recirculate) and use the blower speed to set/maintain your comfort level.
I also ran the rear A/C blower on low most of the week we were in FL but much of the time the 2010-11 Sienna could not quite overcome the FL heat. Running the system on maximum cooling yields the best A/C efficiency (bypasses the reheat/remix airflow path) and FE.
I have a 98 Toyota Sienna with just over 100k miles on it. For the past one year or something, when I turn on air conditioner, it will produce a loud squeaking noise for about 10-15 seconds. The harder you step on the gas pedal the louder and faster (higher frequency) the noise gets. But it diminishes after ~15 seconds. The air conditioner itself works fine, blowing out cold air with no problem. So, could it be alternator? Belt? even battery? Please shine a light. I really don’t want be pushed around by dealer mechanics with some $2,000 estimate. Thank you.
Eimaral
The heat works but when at idle, the air comes out cold. The heat is back instantly as soon as the car is moving. Any ideas on why this is occuring?
Do you have recirc on? Or fresh air?
I would try toggling that to see if it makes a difference.
Wonder if some vaccum hoses are loose and the leak prevents certain trap doors from opening in those circumstances?
I know for the intake a vaccum tube opens a secondary port for more air at high revs.
Did you find out what the problem was? I have the same exactly issue and the dealer still saying there is nothing worng. But it is, sometime it heats ok, sometimes is only COLD air and my children are freezen. I got tired and dont know what to do.
Thanks
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.
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?
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.
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.
Thanks.
You don't say so but I am of the understanding that along with the above, the system also automatically switches to footwell outflow mode, away from "dash" outflow. Only in footwell or partial footwell/windshield mode is any level of warming airflow routed to the interior surface of the windshield.
There is a C-best option, serveral actually, that can be helpful.
1) The A/C can be disabled indefinitely simply by switching it OFF once. It will not activate again, EVER, until you switch it back on. I always have. leave, my A/C disabled throughout the winter period, only have it enabled for actual COOLING requirement.
2) The A/C can be unlinked from automatic operation in defrost/defog/demist mode. Mind is ALWAYS set so.
3) The system can be prevented from switching to cooling mode, dash outflow, automatically once the cabin temperature has risen to, or nearby, the temperature setpoint. There is NO warming airflow to the windshield in cooling mode(***). I do not have this C-best option, '01 F/awd RX300, so I must be fairly diligent in monitoring the system to prevent this switch.
Use of these measures will help dramatically to prevent interior windshield fogging when the OAT is below ~47F and the dehunidification capability of the A/C is mostly, often, non-functional.
If the windshield should fog up, say due to "loading" a couple of wet and sweaty snow skiiers, turn the heat up to MAX and use the windshield defrost/defog/demist mode.
Try to use the A/C and it may, or may not, be functional, but even worse when it subsequently switches off the moisture previously accumulated on the ~10,000 sq. in. of evaporator surface vane area will now become free to evaporate into the cabin.
*** outlet airflow from the upper, dash, and windshield vents will often be as much a 20F lower than airflow from the footwell vents. NipponDenso has a US patent pertaining to their two-layer airflow technique.
That latter mode is how I most quickly defog the interior windshield surface.