PREVOST X3-45 COMMUTER User Manual

SECTION 22: HEATING AND AIR CONDITIONING
36
DOB 1300-1556 | X3-45 Commuter PA-1648 Maintenance Manual First release Oct 2020
5.7.1 Air Conditioning
TROUBLE
CAUSE
Low suction pressure and frosting at dryer outlet.
Clogged filter.
Low Oil Level.
Check for oil leaks and for leaking oil seal. Do not
attempt to check oil level unless system has been
stabilized at least 20 minutes. See oil level
verification.
Excessively cold suction line
And
High superheat
Loss of contact between the expansion valve
bulb and the suction line or sticking of the
expansion valve.
Improper insulation.
Check for corrosion and clean, repair or replace
the valve.
Noisy or knocking compressor.
Check for broken internal parts. Overhaul if
required.
Compressor vibrates excessively.
Check and tighten compressor mounting bolts
and belt tension.
Low refrigerant level
Check for refrigerant leaks and add refrigerant as
required.
Suction pressure rises fast after shutdown.
Check compressor valve for breakage or
damage.
Insufficient airflow.
Dirty or iced evaporator. Dirty air filter. Blowers
inactive. Clogged ducts.
No flow of refrigerant through expansion valve.
Filter dryer is clogged. Remote bulb has lost
charge or expansion valve is defective.
Expansion valve hisses. Bubbles in moisture and
liquid indicator.
Gas in liquid line. Add refrigerant.
Loss of capacity
Clogged filter. Obstructed or defective expansion
valve.
Superheat too high.
Reset superheat adjustment. Check for clogged
external equalizer line, or filter dryer.
Reduced airflow:
a. Dirty or clogged air filter;
b. Evaporator motor inoperative; or
c. Plugged return air ducts.
Dirty or iced evaporator coil. Clean air filter
screen. Check return ducts for obstructions.
Check blower motor.
Frequent starting and stopping on low-pressure
control switch.
Lack of refrigerant. Check for leaks. Recharge.
Compressor intermittently starts and stops.
Intermittent contact in electrical control circuit.
Compressor valves not in operating position.
Non-condensable in the refrigeration system. Leak on system, system in vacuum in low temp.
Specific symptom, pressu
re in system will not
correspond to ambient temperature on shutdown.
Only non-condensable will cause this.
(Example: Pressure of idle R-
134a system in
80°F (26.6°C) room should be 86.4 psi (595.7
kPa). See temperature chart in this section.)
An evaporator
just does a proper cooling job
without sufficient air. Shortage of air can be
caused by the following:
o Dirty filters; or

PREVOST X3-45 COMMUTER Specifications

General

Engine	Volvo D13
Transmission	Allison B500
Fuel Type	Diesel
Length	45 ft (13.7 m)
Width	102 in (2.6 m)
Horsepower	500 hp
GVWR	54, 000 lbs
Height	141 in