Supplemental Climate Control - Overview: Overview
WARNING: This page is about a different car, the 2016 Ford Transit Connect. However, it is still accessible from the selected car via links, so may be relevant.
The climate control system uses the front electric booster heater to heat the passenger compartment during low ambient temperatures when the heater core cannot provide sufficient heat due to low engine coolant temperatures. Once the engine coolant reaches a sufficient temperature to heat the passenger compartment, the climate control system stops using the front electric booster heater.
The climate control system uses the rear electric booster heater to heat the rear passenger compartment in low ambient temperatures. The rear passenger compartment does not have a traditional heater core that uses engine coolant. The rear electric booster heater is only available on longwheel base vehicles.