Climate Control Unit Description

WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

The climate control unit controls air mixture, air intake, air flow mode and fan speed.
The following heater and A/C related functions are controlled by the PCM:
- A/C relay (A/C relay controls A/C compressor magnetic clutch.)
- Condenser fan
- Idle-up control (compensates for A/C compressor and blower motor load)
  
  Fig 1: Identifying Climate Control Unit Features
  Courtesy of MAZDA MOTORS CORP.

Defroster control operation

The defroster control starts when the DEFROSTER or HEAT/DEF switch is turned on. When the defroster control starts, air intake mode and A/C ON/OFF are controlled based on the input signal of each switch.
The transition of air intake mode and A/C ON/OFF when the defroster control operates is as shown in Fig 2 .

Fig 2: Climate Control System Operational Flow Chart
Courtesy of MAZDA MOTORS CORP.

Idle-up control operation

Engine speed is controlled via the PCM to prevent poor engine performance caused by the A/C compressor and blower motor operation (increased electrical load) while the engine is idling.
The climate control unit sends A/C and electrical load idle-up signals to the PCM. Based on these signals, the PCM actuates the idle-up device.

Fig 3: Identifying Idle-Up Input & Control Components
Courtesy of MAZDA MOTORS CORP.

A/C compressor idle-up control

The climate control unit sends A/C signals to the PCM which actuates the A/C relay and the idle-up device.

Electrical load idle-up control

When the fan switch is at 3 and 4, the fan switch sends an electrical load idle-up signal to the PCM. Based on this signal, the PCM actuates the idle-up device.