Additional heater control unit
M75
is supplied with the ignition on (INT/A) - pin 1 of connector B
- from additional heater relay
J36
: this receives its power
supply directly from specific fuse line
B38
. The ignition-operated
power supply (INT/A) to the coil comes via relay
R1
, on
a line protected by fuse
F13
: both are contained within
junction unit
B1
.
Pin 2 of connector B of
M75
is earthed.
Pin 3 of connector A of
M75
receives
a signal from the appropriate temperature sensor
K79
, which
measures air temperature within the engine bay. The sensor only
works with the engine running; it receives a reference signal from
alternator (D+). This signal is low (earth) when the alternator
is not turning. When the engine is running, this signal becomes high
(12V) and supplies the sensor.
Pin 6 of connector A controls additional
heater pump
N44
, which is earthed through inertia switch
I50
.
In case of impact, this cuts off the circuit to prevent the danger
of fuel delivery.
Control unit
M75
is equipped with
a self-diagnostic system that may be used by connecting the unit
to connector
R10
through pin 2 of connector A.