Ford Fiesta: Auxiliary Climate Control / Auxiliary Climate Control - System Operation and Component Description. Description and Operation

System Operation

Electric Booster Heater

The electric booster heater ensures that the passenger compartment can be quickly warmed up when ambient temperatures are low. It is a heater element made up of ceramic resistors that is mounted in the heater core and evaporator core housing. It directly heats the airflow into the passenger compartment rapidly in the case of low ambient temperatures.

The current is switched via two relays located in the auxiliary relay box. The electric booster heater power is supplied via a plug-in connection, the ground connection is screwed in.

The electric booster heater only operates while the engine is running and the HVAC temperature control knob is set to full warm. Its usage is controlled by the IPC .

The IPC energizes the electric booster heater relay(s) depending on the following parameters:

• Engine is running
• Engine coolant temperature is below 60 °C (140°F)
• Ambient air temperature is below 10 °C (50°F)
• Sufficient generator capacity is available
• The HVAC temperature control knob is set to full warm.

The electric booster heater has three stages. Only the first stage of the booster heater is switched on at ambient temperatures between 10 °C (50°F) and 20 °C (68°F) and an engine coolant temperature below 70 °C (158°F). All three stages of the booster heater are switched on at ambient temperatures below 10 °C (50°F) and an engine coolant temperature below 70 °C (158°F).

The electric booster heater is switched off when an engine coolant temperature of 70°C (158°F) or an ambient air temperature of 20°C (68°F) is exceeded.