HVAC System - Mechanism & Function: Overview Subaru Outback BP

Mode Door Operation

The servo motor for driving the mode door is installed on the side facing the driver's seat of the heater unit. Operating the mode selector switch sends a signal to the servo motor. In response to the signal, the motor makes a clockwise or counterclockwise rotation to drive the mode door through a link.

When DEF position (1) or DEF/HEAT position (2) is selected, the air conditioning switch automatically turns ON and the recirculation turns OFF.

Scheme 1

Intake Door Operation

The intake door motor is located on top of the intake unit. It opens and closes the intake doors through a rod and a link. When the recirculation switch is pressed (the indicator comes on), the ground circuit of the intake door motor is formed through terminal 2 of the moving contact instead of through terminal 1. This causes the motor to make a rotation to close the doors. Since the moving contact is built into the motor and rotates together with it, the ground circuit of the motor opens when the contact's slot reaches terminal 2. The motor then stops.

When the recirculation switch is pressed again (the indicator goes out), the ground circuit is formed through terminal 1 rather than terminal 2. The motor makes a rotation in the same direction as when the switch is first pressed - but now opening the intake doors - until the moving contacts slot reaches terminal 1.

Scheme 2

OPERATION OF AUTO CONTROL

1. AUTO switch: When this switch is pressed (ON), the air outlet selection, blower fan speed, air temperature, fresh/recirculation switching, and compressor operation are automatically controlled. When the AUTO switch is pressed second time, the compressor operates in the ECON mode. In the ECON mode, the ECM controls compressor operation based on inputs from the intake air temperature sensor. Compressor operating time in the ECON mode is shorter than in the AUTO mode.
2. Temperature set switch: A desired cabin temperature can be set in 0.5°C (0.9°F) increments.
3. OFF/BRIGHT switch: When this switch is pressed, the blower fan and compressor stop and all the indicators go out. Setting the light switch to the or position causes the illuminating icons on the display panel to dim. When traveling with the lights on in gloomy daylight or in twilight, press the OFF switch for 1 second or longer if you feel it is too hard to identify the icons clearly. The brightness comes back to normal.

Scheme 3

1. A/C switch: The air-conditioner turns on when this switch is pressed first and turns off when it is pressed second time.
2. Blower fan switch: Fan speed changes in the order of Lo, M1, M2 and Hi, every time it is pressed.
3. Ambient temperature display switch: When this switch is pressed momentarily, the ambient temperature is indicated on the display for 5 seconds. When this switch is depressed for more than 1 seconds, the ambient temperature is continuously indicated.
4. Defroster switch: Air is directed to the windshield for defrosting when this switch is pressed.
5. Rear defogger switch: Pressing this switch causes the rear defogger to operate for 15 minutes.
6. FRESH/RECIRC switch: Every time this switch is pressed, switching takes place between fresh air introduction and inside air recirculation alternately.
7. Mode selector switch: Pressing this switch changes the outlets to which the air is directed in the order shown below.