The additional heater unit is connected
to the vehicle electrical system through connector
D22
.
This connector, pin 2, 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 3 is earthed.
Pin 1 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.
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 4 of
D22
via
the diagnostic line.