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MAINTENANCE
Crusader
MC-8
['-- .. _GE
===l
6=--7 __ - _-
_-:._o_Air_De_ce_mb_er_,
_19_7 6_] .
MANUAL
Wiring connections to the heating system ther-
mostat are shown in the wiri11g diagram included in
Section 7 (Electrical) of this manual.
A/C
&
HEATER SWITCH
The A/C-Heating switch is fed from blower cut-in
relay when generator is charging.
The selector switch in heat position "A" operates
the central he.ating coach blower at low speed; in A/C
position "B", it operates the following:
1)
Coach blower operates at high speed.
2) Condenser motor is energized.
3) Compressor unloading solenoid and scavenge_
solenoid ·are energized.
4) Condenser blower operates.
AIR CONDITIONING
The Motor Coach-Carrier air conditioning system
is designed to provide a comfortable, healthful at-
mosphere within the coach. A schematic diagram of
the air-conditioning· system is illustrated in Figure
16-10.
A mixture of cooled, filtered, de-humidified fresh
and recirculated air is supplied through wall ducts
located below the side windows. The combination of
outside and recirculated air is continually filtered,
resulting in a clean fresh atmosphere.
The air is drawn from the coach interior through
center
aisle
ducts.
It
is
filtered,
cooled
and
dehumidified by evaporator coil, then passed through
a temperature-controlled heat core. Two blower fans
send the air conditioned air up into the wall ducts.
The system is designed to provide seven tons of
refrigeration
or
84,000
B.T.U.
per
hour
heat
removal.
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!' The major components
required for a closed circuit refrigeration system are
the compressor, evaporator, condenser, receiver tank
and a liquid metering or expansion valve.
The air conditioning system in the Crusader coaches is
the "Closed" type system using "Freon 12" or "Freon
500".
o
The refrigerant flows to the compressor, is com-
pressed to high pressure and reaches a tem-
perature higher than the surrounding air. It is
passed through the air-cooled fins and tubes of
the condenser coil causing the hot, high pressur<"
gas to be condensed into a liquid form.
o
The liquid refrigerant flows to the receiver tank,
then through a filter-dryer where all moisture,
acids and dirt are removed. It is passed through a
moisture
indicator
which
indicates
if
any
moisture is present in the system.
o
By its own pressure, the liquid refrigerant flows
through a thermostatic-controlled expansion
valve where reduced pressure causes it to become
a low temperature, low pressure liquid.
o
The cold low pressure refrigerant passes through
the evaporator coil, 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.
The success of the air-conditioning system depends
on retaining the conditioned air within the coach. All
windows and intake vents should be closed. An
opening approximately eight inches square could
easily neutralize the total capacity of the system.
Another cause of inadequate cooling is dirty coils
or filter. Dirt acts as an insulation and is also a
restriction to the air flow.
The refrigeration load is not constant and varies or
is affected by outside temperatures, relative humidity,
passenger load, the number of stops, etc. The com-
pressor will load or unlo~d depending ~rn operating
conditions.
The
following
rnformat10n
on
the
operating conditions is only approximate and will
vary with conditions:
Oil Level in Compressor ........ I /2 of sight glass
Freon Level in Receiver ....... I /2 of lower glass
Speed of Engine -
Fast Idle .. Approx. 900 r.p.m.
MANUAL SWITCH CONTROLS
I.
Temperature Rheostat -
Located on the switch
panel to the left of the driver. It controls the air
temperature in the coach during both heating and
air conditioning.
2.
Air Con./Heating Switch -
Located on the panel
to the left of the driver. In "A/C" position, the
air-conditioning system is energized and func-
tions as required. In the "Off' position, the con-
denser and evaporator fans are shut off. In the
"Heating" position, the evaporator fans are at
"Low" speed and the air-conditioning com-
pressor is unloaded.
FAST IDLE
The fast epgine idle can only be used when the
coach is stationary and the emergency parking brakes
are _applied.
'
The feature consists of a fast idle switch on the
driver's switch panel, an air valve in the engine co_m-
partment and an air cylinder mounted on the engme'
governor.
Placing the fast idle switch "ON", eneq~izes t~e air
valve which lets air pressure to the a!f cylmder,
causing the governor-operating lever to be mo_v_ed to
the fast idle position. To eliminate the poss1b11Ity of
engine damage, the accelerator cannot be operated
when the fast idle switch is closed.
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