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Question On Rx 01 Heater Controls


kcossabo
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The heater controls seem confusing on the RX. :whistles:

I have a ‘Auto’ button that reacts to the temperature setting, but usually always sets to blow on the floor. :(

I can select the placement of the blower, feet, dash, front window or combinations.

I can dial the fan speed.

I can hit a different button for just front window.

Here is the confusion;

I select AUTO, and then dash/feet. The heater still follows the temperature, even though the ‘AUTO’ light is off. :wacko: If I dial the fan it then just locks on the blower, and stops following the temperature, but there is no light indicating that it is not going to follow the temperature. :blink:

If I leave it in the selected mode of dash/feet (in the auto-like mode), the blower does not come on until the engine heats, then it comes on 90% full. If I then press, AUTO the fan drops to 1 bar or low? :o

Is this normal :blushing: or is m heater controller broken :o . My Camry would shut off AUTO Temperature as soon as a blower direction was selected, but would turn the fan on full when heat started…..

Thanks

Sorry if this is confusing 

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The heater controls seem confusing on the RX.  :whistles:

I have a ‘Auto’ button that reacts to the temperature setting, but usually always sets to blow on the floor.  :(

I can select the placement of the blower, feet, dash, front window or combinations.

I can dial the fan speed.

I can hit a different button for just front window.

Here is the confusion;

I select AUTO, and then dash/feet. The heater still follows the temperature, even though the ‘AUTO’ light is off.  :wacko:  If I dial the fan it then just locks on the blower, and stops following the temperature, but there is no light indicating that it is not going to follow the temperature.  :blink:

If I leave it in the selected mode of dash/feet (in the auto-like mode), the blower does not come on until the engine heats, then it comes on 90% full. If I then press, AUTO the fan drops to 1 bar or low?  :o

Is this normal  :blushing:  or is m heater controller broken  :o . My Camry would shut off AUTO Temperature as soon as a blower direction was selected, but would turn the fan on full when heat started…..

Thanks

Sorry if this is confusing 

My 04 does the same way as you described as well as my 99 4-Runner! I do it all the time--hit Auto then select where I want it to blow and adjust Temp as needed!

When the engine is cold and its on Auto--its not going to blow cold air, so it waits till the Engine temp comes up a little and starts feeding you warm air a little at a time. If you got the temp to Dialed up to HOT, its going to wait till the motor is nice and warm then blast you with air till you are warm enough.

So its acting normal from what you described....

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If you press "auto" (ONLY!) then all HVAC functions, outlet flow, blower speed, and temperature setpoint, will be controlled automatically. If you then manually select any one of these functions then that function, ALONE, will go into the selected manual mode. All others will remain automatic.

In automatic mode, the "auto" indicator lit, the blower will not start until the engine water jacket temperature rises to 130F.

If the passenger cabin is extraordinarily cold then the blower speed will move from just slightly on to full blast within just a few moments. Once the cabin air temperature approaches your setpoint the blower will slow and the level of heating will be reduced. Once the cabin temperature gets fairly close to your setpoint the system will switch to combined foot/dash and then into dash, cooling mode, alone.

If you have just started the car and it is still cold, engine and cabin, and you switch the airflow mode to windshield or combined windshield/footwell then the blower will go on full blast on the assumption taht the windshield needs to be defogged.

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A/C runs even in COLD climates...

SOP....NORMAL!

Well, at least for the idiots at Toyota, Lexus, NipponDenso, Denso US, and most other asian car manufacturers.

When the switch was made back in the early ninties to the new refrigerant a few things had to be redesigned to make up for the loss of efficency.

One of the most major things was to reduce the amount of flow-thru air through the vehicle and out the exhauster port. The idea being that once the air is "conditioned" keep it inside the car longer. That worked just fine during the summer months but led to the build up of too much moisture within the "closed" passenger cabin during the winter months.

So, run the A/C constantly and sometimes (not nearly always) it helps to "dry" the incoming airflow and prevent windshield condensation.

ALL system airflow is first passed through the A/C evaporator and thereby CHILLED to as close to the evaporator cooling vane regulated temperature of ~33F as conditions (blower speed, evaporator density/efficiency, etc.) allow. Then a varying portion of the chilled airflow is routed through the HEAT exchanger, such that when remixed with the other flow you get system outflow air that is warming or cooling as conditions warrant.

If the airflow entering the A/C evaporator has a high enough relative humdity, RH, then some of the airborne water vapor will be "squeezed" from the air mass as it is chilled.

Later Lexus (and Toyota) have added several c-best options to improve the wintertime performance of these systems.

In the 2001 RX300 you can have the dealer set a c-best option that allows you to completely disable the A/C through all restarts by simply turning it off manually ONCE. It will then be disabled until you enable it by turning it on.

Another C-best option as of 01 was the ability to inlink the A/C from operating automatically (with no indication to the driver) in defrost/defog/demist mode.

By 04 a third C-best option was added which when set allows the system to continuously warm the windshield during cool or cold weather operations.

Absent the use of this C-best setting the system will automatically switch into cooling mode, airflow from the dash outlets only, once the cabin temperature has neared or reached your comfort (temperature setpoint) level. In cooling mode NO warming airflow reaches the interior surface o fthe windshield to keep it warmed and thereby hopefully above the cabin atmosphere's dewpoint.

Keeping the A/C disabled and warming the windshield continously in this manner dramatically reduces the possibility of encountering the instances of sudden and unexpected windshield fogging that these vehicles (NipponDenso and Denso US HVAC designs) are famous for.

Oblique information at:

http://www.airsept.com/eed.html

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