Electric fan unit
By-pass the pressure switch (place jumpers across the two terminals of the pressure switch and the 2 leads of the fan
unit)
If the fan operates: the pressure switch is defective
If the fan does not operate: a) check the fuse;
b) check the relay.
Tracing faults in the electric fan unit
Fault Causes Action
Fan does not start Defective pressure switch
Replace pressure switch
Defective relay
Replace relay
Defective electrical or mechanical
Replace fan unit
part of motor
Relay
place a jumper across terminals 30 and 87a; if the fan comes into operation, the relay needs to be replaced.
Water dripping from the points at which condensate drain lines are connected to the
conditioning unit
The problem can be overcome by loosening the clip that fastens the drain line to the cab upright and pulling the tube
downwards, so that the water can run away freely.
systems
air conditioning
Switching on the air conditioning
Electromagnetic coupling
Pressure switches
The system is activated by way of the 3 speed electric
fan switch.
Once the potentiometer is moved beyond the initial
contact, a voltage of 12 V is generated between terminal
B (red wire) and the brown wire terminal of the poten-
tiometer.
Engagement and disengagement is piloted by the tem-
perature control potentiometer, and by the pressure
switch located at the demoisturizing filter which cuts in
respectively at: 2 bar and 27 bar.
Pressure switch (positioned on demoisturizing filter)
Comprises 3 switches:
— 1 controlling minimum pressure
— 1 controlling maximum pressure
— 1 controlling the electric fan of the condenser. The
electric fan unit is interlocked to the pressure switch,
which is set:
- to close the circuit at 15 bar
- to open the circuit at 11 bar
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