HEATING AND VENTILATION (Description): DESCRIPTION AND OPERATION (page 4 of 10)

HEATING AND VENTILATION

80-6

DESCRIPTION AND OPERATION

Control flaps
Control flaps are installed in the heater assembly to control the temperature and distribution of air. Blend flaps control 
the temperature and distribution flaps control the distribution.

Temperature and distribution control

Figure shows flaps set for medium heat to face level and footwell outlets

1 Windscreen/Side windows outlet
2 Heater assembly casing
3 Air inlet
4 Heater matrix

5 Front footwells outlet
6 Rear footwells outlet
7 Face level outlet

Blend flaps:Two sets of three blend flaps, one LH and one RH, regulate the flow of air through the heater matrix and 
a heater matrix bypass, to control the temperature of the air leaving the heater assembly. The two sets of blend flaps 
operate independently to allow different temperatures to be set for the LH and RH outlets.

Each blend flap is attached to a spindle. The end of each spindle extends through the side of the heater casing and 
is attached to a common lever mechanism on the related side of the casing. A control cable is installed between the 
lever mechanism and the related temperature knob on the control panel. When the flow is split between the bypass 
and the heater matrix, the two flows mix downstream of the heater matrix to produce an even air temperature at the 
individual outlets.

Distribution flaps: Separate distribution flaps are installed to control the flow of air to the footwells,  windscreen/side 
windows and the LH and RH face level outlets. The distribution flaps are attached to spindles that extend through the 
RH side of the heater casing and are attached to a common lever mechanism. A control cable is installed between 
the lever mechanism and the distribution knob on the control panel.