Timed Climate Control Operation

When the ATCM receives a timed climate control start request, its response depends on the ambient air temperature:

• If the ambient temperature is 16 °C (61 °F) or more, the ATCM initiates parked ventilation and:
  • Operates the blower at 47 % of maximum speed
  • Operates the distribution doors in the heater assembly to direct the air to the face level outlets.
• If the ambient temperature is less than 16 °C (61 °F) and more than -20 °C (-4 °F), the ATCM initiates parked heating and:
  • Energizes the changeover valve
  • Sends a LIN bus message to activate the FFBH
  • Operates the blower at 47% of the maximum speed
  • Operates the distribution doors in the heater assembly to direct the air to the footwells for approximately 30 seconds. After 30 seconds, depending on the ambient air temperature the air is directed to either only the windshield, or to both the footwells and the windshield.
• If the ambient temperature is -20 °C (-4 °F) or below, the ATCM sends a LIN bus message to activate the Fuel Fired Booster Heater (FFBH), but leaves the changeover valve de-energized and does not operate the blower or distribution doors. Heated coolant is circulated around the engine and heater core to heat the engine and improve engine starting. Once the FFBH coolant temperature is above a suitable threshold the blower is switched on and passenger compartment heating commenced.

The Fuel Fired Booster Heater (FFBH) will only activate in timed climate control if the following threshold conditions are met:

• Pre-burn battery voltage check: The voltage at the FFBH terminals is above 11.5 V.
• Pre-burn coolant temperature check: The coolant temperature within the FFBH is less than 15 °C (59 °F)
• Pre-burn fuel level check: The fuel level value, stored in the FFBH at ignition off, above 7.5 liters (1.98 US gal).

The fuel level value stored within the FFBH is only updated when the engine is running. When starting the FFBH in timed climate control with the engine off, the fuel level value used in the FFBH calculations will be that stored at the ignition off event. It is therefore possible for the FFBH to fail to operate in timed climate control if the engine was stopped with a low fuel level. If the fuel tank is subsequently refueled, the FFBH stored fuel level will still read low if the engine has not been started since refueling.

After 30 minutes, or if timed climate control is selected off with the TS or FFBH remote control, the ATCM discontinues timed climate control operation.

If parked ventilation is active, the ATCM:

• Switches off the blower
• Returns the distribution doors to the previous settings.

If parked heating is active, the ATCM:

• Sends a LIN bus message to de-activate the FFBH.
• Switches off the blower.
• Returns the distribution doors to the previous settings.
• After 3 minutes, de-energizes the changeover valve.