Hvac System Testing And Troubleshooting; On Demand Activation Of Hot Water Circulating Pump; Temperature Sensors - PREVOST H3-41 Maintenance Manual

clamps over the motor and secure with
mounting bolts.
2. Connect electrical wiring to the pump motor.
3. Open both shutoff valves.
4. Fill the cooling system
instructed in this section under 6.4.4 Filling
Heating System and then bleed the system
as previously instructed in this section.
5. HVAC SYSTEM 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
understand section 06: ELECTRICAL of this
manual under "Troubleshooting And Testing The
Multiplex Vehicles"
Switches And Sensors".
included in these paragraphs is necessary for
troubleshooting the HVAC system on Multiplex
vehicles.
5.1 ON DEMAND DISPLAY OF A/C
SYSTEM HIGH AND LOW SIDE
PRESSURE
Refrigerant pressures can be displayed in the
Driver Information Display (DID) by selecting
"Gauges" menu and pressing the down arrow to
the fifth displayed screen.
A/C Compressor Pressure
Displays the A/C system's suction pressure
value (LoS= low side) and discharge pressure
value (HiS=high side).
NOTE
as previously
circuitry, read and
and "Test Mode For
The information
PA1621 Maintenance Manual All Series | Revised February 2019
SECTION 22: HEATING AND AIR CONDITIONING
When starting the A/C compressor, allow
enough time before checking pressures in
order to give the system a chance to build its
pressure. During the first 3 seconds after
startup, the compressor is active on 4
cylinders and the A/C valve is open regardless
of the pressure readings.
5.2 ON DEMAND ACTIVATION OF HOT
WATER CIRCULATING PUMP
In Diagnostics/Vehicle Test mode on the DID,
the heating system circulating pump can be
turned on manually by selecting ACTIVATE
HVAC PUMP command. This feature allows
verification of the circulating pump when inside a
garage. This is also useful when working on the
heating system to remove air pockets trapped in
the system.
In normal operation,
circulating pump operates only when the
ambient temperature is 50°F or lower.
5.3

TEMPERATURE SENSORS

The following table
troubleshooting the
sensors:
1) Driver area temperature sensor (SE21);
2) Passenger area temperature sensor (SE25);
3) Outside air temperature sensor (SE20).
NOTE
The driver's area air temperature sensor is
located below the dashboard, just ahead of
the driver's right knee.
NOTE
VIP vehicles equipped with Small HVAC
System have two air temperature sensors; the
driver's area temperature sensor (same place
as coaches) and the exterior temperature
sensor located behind the reclining bumper.
the heating system
can be used for
following temperature
45