412-04 Control Components: Description And Operation (page 5 of 21)

LH and RH Temperature Switches: Adjusts the nominal temperature settings of the LH and RH sides of the 
passenger compartment. The switch can rotate through 270°, between full cold and full hot. The switch surrounds 
are graduated in 2° increments between 16 and 28 °C. Minor detents define 1 °C steps over the range of the 
switch. Amber LED's in the switch surround illuminate to indicate the temperature setting. When maximum cold is 
selected, the ATCM also automatically sets the air source to recirculated air, blower speed to maximum and 
distribution to face. When maximum hot is selected, the ATCM also automatically sets the air source to fresh air, 
blower speed to maximum and distribution to footwell.  
LH and RH Seat Heater Switches: Activates the heater elements in the seat cushion and seat back at one of two 
heat levels. The first press of the switch energizes the heater elements at the higher heat setting and illuminates 
two LED in the switch. A second press of the switch sets the heater elements to the lower heat setting and 
extinguishes one of the LED's. A further press of the switch de-energizes the heater elements and extinguishes 
the second LED. The seat heaters remain on until selected off or the ignition is switched off.  
Blower Switch: For manual adjustment of blower speed. The switch can rotate through 240°, from off to 
maximum speed. Eight primary detents define the off position and seven blower speeds. Minor detents define 
small steps between the primary detents. When blower speed is manually adjusted, amber LED's in the switch 
surround illuminate to indicate the selected blower speed. The LED's remain off when blower speed is under 
automatic control.  
Automatic Mode Switch: Activates the automatic modes for the A/C system, blower speed and distribution. 
Separate amber LED's in the automatic mode switch illuminate to show when the blower and the distribution are in 
automatic mode. Manually selecting the blower speed or a distribution switch extinguishes the related LED.  
Programmed Defrost Switch: Activates a program that automatically selects: inlet air to fresh air; distribution to 
screen only; blower to speed 5; rear screen heater on; windshield heater on (where fitted), A/C system to 
automatic mode. An amber LED in the switch is illuminated while the defrost program is active.  
Windshield Heater Switch: Energizes the windshield heater for a set time period, until the switch is pressed 
again or until the engine stops, whichever occurs first. An amber LED in the switch is illuminated while the heater 
is on.  
Rear Window Heater Switch: Enabled only with the engine running. Pressing the switch energizes the rear 
window heater for a set time period, until the switch is pressed again or until the engine stops, whichever occurs 
first. An amber LED in the switch is illuminated while the heater is on.  
Auxiliary Climate Control Switch: Cycles the auxiliary climate control system through the three operating states 
of manual mode, automatic mode and off. Two amber LED's in the switch illuminate to indicate the operating 
state: one LED is illuminated for manual mode and two are illuminated for automatic mode.  
Off Switch:Switches off all of the functions controlled by the ATCM (all tell-tale LED's are extinguished). The 
temperature blend door is set to the full cold position (if the A/C system is in the automatic mode, if the A/C system 
is in the economy mode the current door position is retained); the air source is set to recirculation; the current 
distribution settings are retained; the blower speed is set to zero. Where fitted, the seat heater switches and the 
auxiliary climate control switch can still be operated without re-activating the ATCM. The ATCM is re-activated, 
with all functions in the previous operating state, by a second press of the off switch or by pressing the economy 
switch. The ATCM can also be re-activated, with the associated effect, by the following switches: The automatic 
mode switch. Any air distribution switch. The blower switch. The programmed defrost switch. The recirculation 
switch. 

The automatic mode switch.  
Any air distribution switch.  
The blower switch.  
The programmed defrost switch.  
The recirculation switch.  

Economy Switch: Reduces the A/C compressor output to a minimum displacement condition x 5%, reducing the 
engine load required to operate the A/C compressor. An amber LED in the switch is illuminated when the 
economy mode is selected on.  
Recirculation Switch: For selection of fresh or recirculated air. On models without pollution sensing, an amber 
LED in the switch is illuminated when recirculated air is selected. On models with pollution sensing, the 
recirculation switch incorporates two amber LED. The first press of the switch sets the recirculation flaps to 
automatic mode and illuminates one LED. A second press of the switch manually selects recirculated air and 
illuminates the second LED. A further press of the switch manually selects fresh air and extinguishes the two LED. 
Distribution Switches (Windshield, Face and Footwell): For manual selection of air distribution in any 
combination of windshield, face and footwell outlets. Each switch has a LED which illuminates when the related 
distribution mode is selected.  
 

Inputs and Outputs 

Four electrical connectors provide the interface between the ATCM and the vehicle wiring. 
 
The control system sensors provide hardwired inputs to the ATCM. The ATCM also uses the LIN bus to communicate 
with the auxiliary climate control system and the door motors in the heater assembly, and the medium speed CAN bus to 
communicate with other control modules on the vehicle. For additional information, refer to   

Communications