Section 22: HEATING AND AIR CONDITIONING
PA1562
9
FIGURE 14: PASSENGERS' SECTION AIR FILTER 22306
CAUTION
Do not use high pressure water jet to avoid
damaging filter.
CAUTION
Be sure not to reverse filter upon installation.
4.4 OVERHEAD COMPARTMENT FAN AIR
FILTER
A/C evaporator coils may be installed in both
overhead compartment air systems. Only the air
filters are serviceable. The air filters are
accessible from inside the overhead
compartments. Slide out the filters, then back
flush with water, dry with air and replace. This
procedure should be done every 12,500 miles
(20,000 km) or once a year, whichever come
first.
If A/C units were installed, ball valves are added
on supply and return lines in the engine
compartment. They have service port to
evacuate the A/C overhead compartment circuit.
When work has to be done on an evaporator coil
unit, it will be easier to remove it and repair it on
a bench.
FIGURE 15: OVERHEAD COMPARTMENT FAN AIR
FILTER
22201
5. HVAC SYSTEM PARTICULARITIES,
TESTING AND TROUBLESHOOTING
Before undertaking any troubleshooting on the
HVAC system, study the appropriate wiring
diagrams to get a complete understanding of the
HVAC components circuitry, read and
understand section 06:ELECTRICAL of this
manual under "Troubleshooting And Testing The
Multiplex Vehicles" and "Test Mode For
Switches And Sensors". The information
included in these paragraphs is necessary for
troubleshooting the HVAC system on Multiplex
vehicles.
5.1 HVAC SYSTEM AND TEST MODE FOR
SWITCHES AND SENSORS
When in switch/sensor test mode (see Section
06: ELECTRICAL for complete information), the
A/C compressor HI and LO pressure values are
displayed one after the other instead of the
outside temperature in the telltale panel LCD
display. This feature can be used when the
vehicle is traveling to check the A/C compressor
pressure values.
NOTE
When starting the A/C compressor wait 5
seconds before checking pressures in order to
give the system a chance to build its pressure.
During the first 5 seconds after startup, the
compressor is active on 6 cylinders and the
A/C valve is open regardless of the pressure
readings.
In test mode, with the parking brake applied and
the passenger set point set to a value higher
than 64°F (18°C), the hot water circulating pump
is not set to OFF as it would normally do when
the outside temperature gets above 50°F
(10°C). This feature allows verification of the
pump when inside a garage. This is also useful
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