Electric Booster Heater Operation

For diagnostics on front or rear electric booster heaters, Refer to: Climate Control System - Vehicles With: Dual Automatic Temperature Control (DATC) . Refer to: Climate Control System - Vehicles With: Electronic Manual Temperature Control (EMTC) .

The electric booster heater electronics activate depending on a PWM signal generated by the BCM. The overall heating power of the heating elements is linearly proportional to the PWM signal. If the PWM signal is below 10% or above 95%, the electric booster heater is not activated. The electrical system will prioritize other electrical loads over the rear electric booster heater and therefore may not supply enough electrical power to the rear electric booster heater.

Front Electric Booster Heater 

If the front HVAC controls have been switched to the highest setting, the HVAC control module sends an electric booster heater ON request signal to the BCM via the MS-CAN. The BCM responds by sending a PWM signal to the front electric booster heater if the operating parameters have been met.

Front electric booster heater operating parameters:

• Engine coolant temperature is below 64 °C (147 °F)
• Ambient air temperature is below 8 °C (46 °F)
• Sufficient generator capacity is available

The front electric booster heater is deactivated when an engine coolant temperature of 66 °C (150 °F) or an ambient air temperature of 10 °C (50 °F) is exceeded.

Rear Electric Booster Heater 

The rear electric booster heater is part of the rear climate control system located under the driver front seat and extending back under the 2nd row LH side passenger floor. When the RHVAC controls are set to a hot temperature, the RHVAC control module sends a request signal to the BCM via a hardwired circuit. The BCM responds by sending a PWM signal to the rear electric booster heater. The higher the temperature setting, the greater the PWM signal.