The relay
J20
controls the compressor
engagment circuit.
The relay is supplied by relay
R1
:
line controlled by the ignition INT/A, protected by fuse
F15
:
both are housed in the junction unit
B1
.
The supply for the relay
R1
comes
from the direct line of the maxifuse
J/B1
of
B5
,
whilst the coil is supplied by the line (INT/A) protected by the
fuse
B26
: this line also supplies the switch unit
H80
,.
via fuse
B27
.
The relay
J20
coil is suppiled by
the line protected by fuse
B39 See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT
.
Press the appropriate button on unit
H80
to sends a signal to 4-stage pressure switch K10:
This, in turn, if the pressure in the circuit
is correct, does not interrupt the signal which reaches the engine
control unit
M10
(pin 60 of connector A).
Control unit
M10
uses its own internal
software to send a signal (from pin 18 of connector A) to activate
the compressor which energizes the relay
J20
.
The relay operates the solenoid valve, at
12 V, which switches on the air conditioning compressor
L20
.
The second signal energizes the relay
J34
coil which activates the first speed for the fan
N85
, according
to the description
See E6020 AIR CONDITIONING
.
The fan operates at the first speed if the
button for engaging the compressor is pressed, even if the control
knob
H81
is in position '0'.