Den, Here is a description of the heater unit that I got from Rave.
The heater unit consists of a housing containing a
heater matrix which is connected to the engine cooling
system. As water is circulated continuously through
the heater matrix, the selection of hot or cold air is
controlled by servo operated LH and RH blend flaps
directing the air through or around the heater matrix.
The LH and RH blend flaps operate independently to
allow different temperatures to be set for the LH and
RH air vents. The servo operated distribution flaps
control the flow of air from the heater unit to the outlet
vents. Air distribution is common to both sides of the
vehicle interior.
The two temperature servos and the distribution servo
each incorporate a feedback potentiometer which
provides the Heater ECU with a flap position signal to
enable accurate control of air temperature and
distribution.
Kevin
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