Climate Control Unit
Climate control unit
System overview
1. Heater element
2. Stepper motor temperature left
3. Blower fan in the passenger compartment
4. Stepper motor fresh air/recirculation
5. Power unit
6. Particle filter
7. Stepper motor ventilation and floor (+defroster MCC/STD)
8. Stepper motor temperature right
9. Stepper motor defroster (ECC)
Heater element
The engine coolant flows through the heater element constantly. There is no valve to regulate the flow. The set temperatures are achieved by shutters for the right and left hand sides installed upstream of the heater element. The control the amount of air to be warmed. There is also shutters downstream of the heater element that guide the airflow to the correct air vent.
Blower fan in the passenger compartment
All the systems have stepless electronic blower fan control. When AUTO (Electronic climate control (ECC)) is engaged the Climate control module regulates the blower fan speed to the control setting and the vehicle speed.
The blower fan speed is adjusted to the vehicle speed up to 160 km/h (99 mph) at which point the fan stops. At higher speeds the air intake is adjusted by the fresh air shutter.
Before the fan starts the Climate control module runs a diagnostic check. This is carried out by the power unit supplying the fan with 12.5 volts for 0.3 second and then with 6.5 volts for another 2.7 seconds. The 0.3 seconds long supply pulse has the task of overcoming the resistance of any ice or snow that may otherwise block the fan wheel, at the same time the diagnostic whether the fan is blocked. In the next 2.7 seconds the fan power consumption is measured. After the diagnostic check the fan gradually returns to the selected speed.
Blower fan run on
Blower fan run on reduces the amount of water remaining in the evaporator.
Run on is time governed and controlled by a timer located in the central electronic module (CEM) which ensures that power supply to the Climate control module is activated for 50 minutes after the ignition has been turned to positions 0 or I. This means that the Climate control module is put in the run on position and starts a check program to dry out the evaporator. Run on is activated for 7 minutes.
The function is only activated as a result of a customer complaint. Activation is carried out by programming customer parameters via VIDA.
Particle filter
The particle filter is standard and is mounted downstream of the blower fan so that even recirculated air is cleaned. The particle filter should be replaced every 15,000 km or 2 years. The particle filter was previously available as an option or as standard (market dependent), but then mounted at the air intake. This meant that recirculated air was not cleaned.
Shutter motors
The Manual climate control (MCC) and standard (STD) systems previously had cables between the air distribution controls and the floor, defroster and ventilation shutters. The manual system is now replaced by the same type of controls used on the Electronic climate control (ECC).
- All shutter motors are the stepper type, which means that angle of turn and speed is controlled electronically.
- Manual climate control (MCC) / standard (STD) has 4 stepper motors which control the following shutters:
- Ventilation/floor/defroster via a link system.
- Recirculation and fresh air via a link system.
- Temperature left.
- Temperature right.
- A stepper motor controlling the defroster is introduced on the Electronic climate control (ECC).
Stepper motor
Previously DC motors were used. The advantages with the stepper motors used is that:
- The stepper motor has no carbon which wears.
- No sensor is required to determine shutter position.
- The turning degree of the motor is determined by the number of control steps from the.
- The stepper motor has a higher holding torque.
The wiring between the stepper motors and the Climate control module consists of 4 cables for supply voltage and direction control and a separate cable for each motor which controls which motor is to be activated.
In a DC motor the length of time a motor is supplied with power determines how many revolutions the motor shaft turns. In a stepper motor it is the number of control steps from the Climate control module. Only when the motor goes to an end position is the number of steps of no importance. The stepper motor are self-adjusting.