Heating And Ventilation: Heater: Notes

Courtesy of JAGUAR CARS, INC.

The heater controls the temperature of the air supplied to the distribution ducts, as directed by the automatic temperature control (ATC) module. The heater is installed on the vehicle center-line, between the instrument panel and the engine bulkhead. The heater consists of a casing, formed from a series of plastic molding, which contains an evaporator, heater core and control doors. Internal passages integrated into the casing guide the air through the casing and separate it into two flows, one for the left-hand (LH) outlets and one for the right-hand (RH) outlets.

When the air conditioning (A/C) system is operating, the evaporator cools the air entering the heater.

The heater core provides the heat source to warm the air being supplied to the distribution ducts. The heater core is an aluminum two pass, fin and tube heat exchanger, installed across the width of the heater housing. Two aluminum tubes attached to the heater core extend through the engine bulkhead to connect with the engine cooling system. When the engine is running, coolant is constantly circulated through the heater matrix by the coolant pump. On vehicles with a FFBH (fuel fired booster heater), when the FFBH is active the coolant flow is assisted by an electric circulation pump. Refer to Auxiliary Heater information.

Two temperature blend doors, one left-hand (LH) and one right-hand (RH), regulate the flow of air through the heater core to control the temperature of the air leaving the heater. On the automatic system, the two temperature blend doors operate independently to allow different temperatures to be set for the left-hand (LH) and right-hand (RH) outlets. On the manual system, the temperature blend doors are coupled together and produce a common temperature for the left-hand (LH) and right-hand (RH) outlets.

Air Flow Through Heater

Courtesy of JAGUAR CARS, INC.