Automatic Temperature Control (ATC)

The Automatic Temperature Control (ATC):

Is addressable with the DRBIII®
Communicates over the Programmable Communication Interface Multiplex System (PCI) Bus.
Can be operated in a manual mode.
Uses an integral-mounted aspirator motor and in-car temperature sensor to maintain occupant comfort levels when set in an automatic mode.
Provides a request over the PCI Bus to the BCM when door actuator (blend, mode, recirculation) operation is desired.
Provides a request over the PCI Bus to the BCM when A/C operation is desired.
Provides a request over the PCI Bus to the BCM when EBL operation is desired.
Provides desired blower motor operating speed data over the PCI Bus to the BCM.

The Body Control Module (BCM):

Drives the ATC status indicators (EBL, A/C, and Recirc) over the PCI Bus.
Remembers the last temperature setting at power down.
Sets the initial temperature setting via the PCI Bus when the ATC is powered up.
Drives the electric door actuators (mode, blend, recirculation).
Controls blower motor operating speed.
There are 14 blower speeds when the ATC is in manual mode and infinite speeds when the ATC is in automatic mode.
Monitors the blower motor for a stall condition via a blower speed sense circuit.
Sends a request over the PCI Bus to the PCM when A/C operation is desired.
Uses sun load sensor data to maintain occupant comfort levels when the ATC is set in an automatic mode.
Uses Evaporator Temperature Sensor data to prevent evaporator freeze up while maintaining optimum cooling performance.

Blower Motor Operation:

The Blower Power Module provides the blower motor with power and a path to ground. It also sends a blower control signal to the BCM. The BCM constantly receives desired blower speed data from the ATC over the PCI Bus. Using this data, the BCM processes the blower control signal which sets the speed that the Blower Power Module will run the blower motor.

The ATC HVAC system uses: