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SUVs Toyota Highlander Toyota Highlander Heating Ventilation and Air Conditioning
107 messages, Last post on Nov 16, 2009 at 5:13 PM
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Replying to: slowcar (Oct 10, 2009 5:56 am) Air inlet with a damper door to select fresh intake airflow or recirculate. Fresh airflow is usually taken in at the foot of the windshield on the passenger side (US). Recirculate airflow is taken in from an opening behind the glove box' traditional position. ALL system airflow, regardless of fresh/recirc intake origin, then flows through the pollen filter, the blower ("sucker") and then to, through, the cooling evaporator core. The cooling evaporator core is typically operated at ~34F(***). So if the blower speed is fairly low the airflow temperature at this point might be very close to freezing. The next step is the reheat/remix vane/door. The control system will "set" the position of the vane door such that a selected portion of that just previously cooled airflow will be diverted from the "main" flow path and through the ~180F heater core. Downstream of the heater core the two airflow portions will remix/merge and the end result will be system outlet airflow that is cool enough, sometimes just BARELY cool enough, to maintain the passenger cabin, OVERALL, at your selected temperature setpoint. If you turn the manual control to maximum cooling or the automatic one to the lowest temperature setting then NO airflow will be reheated and the outflow might be discomfortingly COLD. *** Currently no method is used to moderate the operating temperature of the evaporator, mostly in order to take full (but RANDOM) advantage of the evaporator's dehumidification aspects. |
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wwest: few questions. 1) It doesn't seem to be efficient to heat up part of the cold air (+34F) with the +180F heater core and then re-mix it with the original cold air to regulate the temperature. It's like running your house aircond at full speed and then open the windows slightly to maintain the set temperture. p.s. BTW, I thought the car air cond regulates the temperature via the Expansion Valve, where it opens to allow liquid freon from the Condenser to flow to the Evaporator if it wants to cool down the air. When the cabin's air is cool enough this Expansion Valve will be closed; thus no more cooling. Am I wrong? 2) Is there a vane door separately for passenger side and driver side so that on the driver side, the vane door was stuck and won't allow the cold air to go through and mix in with the warm air? If there isn't a separate vane door for the driver side, then why the passenger side's temp is much lower (20F) than that of driver side if both sides share the same vane door? The kicker is that the system had been working no problem until recently !!! So it can't be the problem with the Toyota aircond design.
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Replying to: cpiper (Mar 08, 2008 5:51 am) |
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Replying to: rut (Aug 02, 2009 5:42 pm)
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Replying to: slowcar (Oct 14, 2009 10:52 am) All I know, or think I know, is that the temperature of the evaporator vane surface area is not easily moderated. So we get downstream "moderation" via the remix/reheat vane/door setting. 2. These days, even if you did not purchase a climate control with the L/R different temperature settings the "core" system may still have that capability for purposes of parts commonalty. Then the question becomes is the function being used..? It would make sense to if the radiation sensor indicates the solar radiation heating effects are primarily on the passenger's side then more cooling would/might be routed to that side. A L/R system malfunction is also a possibility. To extend FE I often run my climate control systems on MAX COOLING and recirculate. Then I use the blower speed to regulate the overall cabin temperature. If that still results in too much cooling to my face and upper body I set the outlet airflow to dash/footwell combined or footwell only. That being said.... Climate control systems designed by Denso US, NipponDenso, have shown an unusual propensity for sudden spontaneous fogging of the interior surface of the windshield. So running the driver's side outlet airflow a bit higher than the passenger side might well be something of a corrective measure to help alleviate these instances. |
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Replying to: davidc4607 (Oct 18, 2009 3:21 pm) |
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Probably a straight forward one for you all. I have a 2009 HH - I doubt that it being a hybrid affects this issue. I have the manual heating and air configuration. It's annoying that even with the fan turned to the off position and cabin recirc disabled, I get some mixed air out of where ever the selection knob is pointed. Of course, you can get no air flow in the recirc mode but when the humidity gets high enough in the cabin it automatically goes back to outside air and the air starts coming through again. Is it designed like this - outside mixed air when not in recirc- or is mine broken with a vane that's not closing all the way? We never noticed this in our test drives because it was august and 100f and the A/C was on continuously
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Replying to: bobinco (Nov 15, 2009 3:31 pm)
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Replying to: wwest (Nov 15, 2009 4:31 pm)
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Replying to: bobinco (Nov 15, 2009 7:03 pm) During the winter months the incoming fresh airflow will typically have a lower Rh than the cabin atmosphere. Have you tried routing the incoming airflow to the footwell. Also, during automatic operation the footwell airflow is often as much as 20F warmer than the airflow you get from the dash outlets. Oh, and you can, and should, manually close the leftmost and rightmost dash airflow outlets.
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