Electric Booster Heater Operation

WARNING: This page is about a different car, the 2018 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.

If the interior temperature has been set to HI, or if the heater controls have been switched to the highest setting, the air conditioning system sends an "electric booster heater ON" request signal to the BCM via the MS-CAN. The BCM controls the electric booster heater with a PWM signal.

The BCM activates the electric booster heater depending on the following 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 electric booster heater electronics activates depending on a PWM signal generated by the BCM. Due to the variable switch-on duration, continuously variable temperature control is possible. 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 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.

Component Description

Electric Booster Heater

The electric booster heater is composed of PTC elements and a microcontroller. The microcontroller allows the PTC elements to be activated depending on the PWM input from the BCM.