The additional heater unit is connected
to the vehicle electrical system through connector
D22
.
This connector, pin G, receives a direct
supply through the line protected by the maxifuse
B37, which
also supplies the diesel pre-heating system and by a specific fuse
B38;
pin E is connected to earth.
Pin A of
D22
is connected to the
outside air temperature sensor
K79
which, in turn, receives
the reference supply from the alternator (D+ pin signal): in this
way the signal for the outside temperature is only sent to the additional
heater control unit if the engine is running.
Pin D receives the on signal from the remote
control receiver
M74
.
This receiver is supplied by a direct line
protected by a special fuse
B105
.
Pin B receives the inertia switch
I50
earth signal which cuts off the circuit in the case of an impact
and prevents the dangerous delivery of fuel.
The heater unit control unit is also connected
to the climate control system control unit
M70, via pin F to
operate the fan N85 with the heater switched on.
This operation is managed by the special
relay
J36
.
The passenger compartment air temperature
sensor, located in the controls
H80
, is also operated at
the same time.
The additional heater control unit is equipped
with an autodiagnostic system which can be used: by connecting the
unit to connector
R10: it receives signals from pin C of D22 via
the diagnostic line.