Winnebago 1987-1989 LeSharo Service Manual page 617

DIAGNOSIS OF Ale SYSTEM
CONDITION 8
THERMOSTATIC EXPANSION VALVE MALFUNCTION
(VALVE STUCK OPEN)
LOW SIDE HIGH
LOW SIDE
HAND VALVE
CLOSED
lOW SIDE HOSE
CONNECTED TO
LOW SIDE SERVICE
CONNECTOR
AMBIENT
lEMP.95° F.
HIGH sloe NORMAL
OR SLIGHTLY LOW
HIGH SIDE HOSE
CONNECTED TO
HIGH SIDE SERVICE
CONNECTOR
Complaint
Little or no cooling.
Condition
1. Low side gauge reading too high. Should be
15-30 psi.
2. High side gauge reading normal or slightly
low. Should be 185-205 psi at an ambient
temperature of 95°F. See chart for pressuresat
other ambient temperatures.
3. Discharge air from evaporator warm.
4. Suction hose and evaporator show heavy
sweating.
Diagnosis
Expansion valve allowing excessive flow of
refrigerant through evaporator causing flooding of
evaporator coils.
Testing
1. Check for expansion valve stuck open or
incorrect mounting of temperature sensing
bulb as follows:
a.) Set air conditioner for maximum cooling
and operate the system.
b.) Spray liquid Refrigerant-12 on head of
valve or capillary bulb; note low side gauge
reading. Low side gauge should drop into a
vacuum.
c.) If low side vacuum reading obtained, warm
expansion valve diaphragm chamber with
hand, then repeat test (Step "b").
Correction
1. If expansion valve test indicates valve
operation is satisfactory, proceed as follows:
a.) Clean contact surface of evaporator outlet
pipe and temperature sensing bulb, clamp
bulb securely in contact with pipe.
b.) Operate system and check performance.
2. If expansion valve test indicates valve is
defective, proceed as follows:
a.) Discharge system
b.) Replace expansion valve
c.) Evacuate system using vacuum pump.
d.) Charge system with New Refrigerant-12.
e.) Operate system and check performance.
N4-11