Heater Unit Description

• The heater regulates the airflow mode and the outlet airflow temperature.

Heater core operation 

• A portion of engine coolant is diverted to the inside of the heater core, where it heats the air passing through the core.
  Fig 1: Identifying Heater Core & Radiator Coolant Flow

  Courtesy of MAZDA MOTORS CORP.

Air mix door operation 

• The air mix doors, installed in the heater unit, move to each position: HOT or COLD, by the air mix actuator's operation. As a result, airflow distribution changes.
  Fig 2: Identifying MAX HOT & MAX COLD Air Mix Door Positions

  Courtesy of MAZDA MOTORS CORP.

Airflow mode door operation 

• The airflow mode doors, installed in the heater unit, move to each position: VENT, BI-LEVEL, HEAT, HEAT/DEF, DEFROSTER, by the airflow mode actuator's operation. As a result, airflow mode changes.
  Fig 3: Identifying VENT, BI-LEVEL & HEAT Airflow Mode Door Positions

  Courtesy of MAZDA MOTORS CORP.
  Fig 4: Identifying HEAT/DEF & DEFROSTER Airflow Mode Door Positions

  Courtesy of MAZDA MOTORS CORP.

  Airflow distribution 

  Fig 5: Airflow Mode Distribution Percentages Table

  Courtesy of MAZDA MOTORS CORP.