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AIRFLOW VOLUME CONTROL OPERATION

id074000102600

## Airflow Volume Automatic Control

• Based on the set temperature, the ambient temperature, and sunlight intensity, the climate control unit calculates the blower motor voltage characteristic (AUTO voltage). It compares the differences among this voltage characteristic, and the target temperature (control computation value T2) and then determines the voltage to be applied to the blower motor.

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1 | Transition period
2 | Stable period
3 | When cooling
4 | When heating
5 | Increases/decreases linearly with sunlight intensity
6 | Blower motor applied voltage characteristic
7 | Blower motor applied voltage
8 | Control computation value T2
9 | MAX-HI
10 | MIDDLE-HI
11 | AUTO-HI

### Correction

Coolant temperature correction (warm-up correction)

  • To prevent a large volume of cold air from blowing through the ventilation outlets when the engine is started in winter, coolant temperature control links the blower motor voltage to the rise in engine coolant temperature. However, coolant temperature correction does not operate when the defroster correction is running, when the cabin temperature is above 20 °C {68 °F}, or when airflow is in VENT mode.

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1 | Rise to auto voltage
2 | Blower motor applied voltage
3 | Coolant temperature
4 | Low
5 | High

Mild start correction

  • To prevent a large volume of warm air from blowing through the ventilation outlets when the blower motor is started in summer, the voltage applied to the blower motor is restricted for 3 s after it starts. However, mild start correction does not operate when the passenger compartment temperature is below 20 °C {68 °F}, or when airflow is in any mode other than VENT.

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1 | Rises to auto voltage
2 | Blower motor applied voltage
3 | Time

MAX HOT and MAX COLD correction

  • When the temperature is set to 29.0 (European (L.H.D. U.K.) specs.) or 32.0 (Australian, General (L.H.D. R.H.D.) specs.), the applied voltage of the blower motor is set at AUTO-HI, when at 15.0 (European (L.H.D. U.K.) specs.) or 18.0 (Australian, General (L.H.D. R.H.D.) specs.), the applied voltage of the blower motor is set at MAX-HI. However, when in water temperature correction, MAX HOT correction does not take place.

Correction | Set temperature | Blower motor applied voltage
--- | --- | ---
MAX HOT | 29.0 (European (L.H.D. U.K.) specs.) 32.0 (Australian, General (L.H.D. R.H.D.) specs.) | 12.1 (V): AUTO-HI
MAX COLD | 15.0 (European (L.H.D. U.K.) specs.) 18.0 (Australian, General (L.H.D. R.H.D.) specs.) | B+: MAX-HI

Windshield mist prevention correction

  • To prevent the air blown from the defroster when the heater is started in winter from clouding the windows, the blower motor and the A/C signal output are switched off for 6 s after the ignition is turned to the ON position. This control only operates if the airflow is in HEAT, HEAT/DEF, or DEFROSTER mode.

Start compensation correction

  • When the blower motor is started at 3.2 V, it is run at a voltage of 4.4 V for 2 s to help it stabilize at the target voltage.

Defroster correction

  • To improve defrosting and heating, 2.0 V is added to the AUTO voltage calculated airflow volume automatic control when the defroster switch is turned on.

Fail-safe function

  • If the blower motor is started with more than 4.4 V, a surge will occur and the power MOS FET may burn. To prevent this, the voltage applied to the blower motor is regulated to 4.4 V for 1 s when it is started.

## Airflow Volume Manual Control

• The blower motor (airflow) has seven speeds and is operated by the fan switch.

Fan speed | Switch operation | Control device | Blower motor voltage
--- | --- | --- | ---
1st | Airflow volume automatic control, manual 2nd (-), manual 1st (-) or OFF (+ or -) | →manual 1st | Power MOS FET | 4.4 (V)
2nd | Airflow volume automatic control, manual 1st (+), or manual 4th (-) | →manual 2nd | Power MOS FET | 6.1 (V)
3rd | Airflow volume automatic control, manual 2nd (+), or manual 4th (-) | →manual 3rd | Power MOS FET | 7.8 (V)
4th | Airflow volume automatic control, manual 3rd (+), or manual 5th (-) | →manual 4th | Power MOS FET | 9.5 (V)
5th | Airflow volume automatic control, manual 4th (+), or manual 6th (-) | →manual 5th | Power MOS FET | 10.8 (V)
6th | Airflow volume automatic control, manual 5th (+), or manual 7th (-) | →manual 6th | Power MOS FET | 12.1 (V)
7th | Airflow volume automatic control, manual 6th (+), or manual 7th (+) | →manual 7th | Power MOS FET | B+