Additional heater control unit
M75
is supplied at pin 1 (connector B) directly from the battery. via
the line protected by fuse F23 of the engine compartment junction
unit
B1.
The earth is taken to pin 2 (connector B)
via additional heater relay
J36, switch I20 and relay T1 of junction
unit B2.
When relay
T1 is energised via the line
(15/54) its contact supplies the coil of additional heater relay
J36 via fuse F6. Control unit M75 receives an earth signal via its
contact.
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. The signal becomes
high (12 V) and supplies the sensor when the engine is running.
See E5010 STARTING AND RECHARING
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 emerging.
If the intertia switch is operated it de-energizes
the relay
J36.
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.
See E8010 DIAGNOSTIC MULTIPLE CONNECTOR
.