Section 22: HEATING AND AIR CONDITIONING
PA1562
12
Problem/Symptom Probable Causes Actions
2. Check / reset circuit breaker CB1
3. Check / replace fuse F12
The A/C compressor clutch
does not engage
Module A52 is not powered or is
faulty
1. Check the SYSTEM DIAGNOSTIC menu
of the message center display (MCD).
Select FAULT DIAGNOSTIC and
ELECTRICAL SYSTEM. The message
“Voltage Module A52, Value too Low,
Active” confirms a power problem on the
module
2. Check / reset circuit breaker CB5
3. Check / replace fuse F65
Evaporator fan not
functioning
Circuit breaker CB3 tripped
Module A54 is not powered or is
faulty
Brush problem
1. Check / reset circuit breaker CB3
2. Check the SYSTEM DIAGNOSTIC menu
of the message center display (MCD).
Select FAULT DIAGNOSTIC and
ELECTRICAL SYSTEM. The message
“Voltage Module A54, Value too Low,
Active” confirms a power problem on the
module
3. Check / reset circuit breaker CB5
4. Check / replace fuse F67 , F68
6. CENTRAL AIR CONDITIONING SYSTEM
The schematic of Figure 16 shows the central and
auxiliary A/C systems and their components. The
central system is equipped with a 6 cylinder, 05G
Twin Port Carrier compressor with an air
conditioning capacity of 7½ tons. The receiver
tank and filter dryer are mounted inside the
condenser compartment.
X3 Coaches may be supplied with an auxiliary
A/C system (Fig. 16). Auxiliary A/C system comes
with a 7 cylinder, Sanden SD7 compressor with
an air conditioning capacity of 2 tons.
6.1 A/C CYCLE
Refrigeration may be defined as "the transfer of
heat from a place where it is not wanted to a
place where it is unobjectionable". Components
required for a closed circuit refrigeration system
are shown in Figure 16.
The air conditioning system used on X3 series
coaches is of the "Closed" type using "R-134a".
1. The refrigerant flowing to the compressor is
compressed to high pressure and reaches a
temperature higher than the surrounding air.
It is passed through the air-cooled fins and
tubes of the condenser causing the hot,
high pressure gas to be condensed into a
liquid form.
2. The liquid refrigerant flows to the receiver
tank, then passes through a filter dryer
where moisture, acids and dirt are removed
and then through a moisture indicator which
indicates if any moisture is present in the
system.
3. By its own pressure, the liquid refrigerant
flows through a thermal expansion valve
where the pressure drop causes the
refrigerant to vaporize in a vapor-liquid state
at a low temperature pressure.
4. The cold low pressure refrigerant passes
through the passengers and the driver’s
evaporator coils which absorbs heat from
the air passing over the fins and tubes, and
changes into gas. In this form, the
refrigerant is drawn into the compressor to
repeat the air conditioning cycle.
5. The success of the air conditioning system
depends on retaining the conditioned air
within the vehicle. All windows and intake
vents should be closed. An opening of
approximately 8 in
2
(5162 mm
2
) could easily
neutralize the total capacity of the system.
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