Winnebago 1987-1989 LeSharo Service Manual page 618

DIAGNOSIS OF Ale SYSTEM
CONDITION 9
THERMOSTATIC EXPANSION VALVE MALFUNCTION
(VALVE STUCK CLOSED)
LOW SIDE LOW
lOW SIDE
HAND VALVE
CLOSED
lOW SIDE HOSE
CONNECTED TO
LOW SIDE SERVICE
CONNECTOR
AMBIENT
TEMP. 95° F.
HIGH SIDE LOW
HIGH SIDE HOSE
CONNECTED TO
HIGH SIDE SERVICE
CONNECTOR
1
Complaint
Cooling is not adequate.
Condition
1. Low side gauge reading too low (0 psi or a
vacuum). Should be 15-30 psi.
2. High side gauge reading too low. Should be
185-205 psi at ambient temperature of 95°F.
See chart for pressures at other ambient
temperatu res.
3. Discharge air from evaporator only slightly
cool.
4. Expansion valve inlet may show heavy
sweati ng or frost.
Diagnosis
Expansion valve restricting refrigerant flow due to
clogged screen, stuck valve, or temperature sensing
bulb having lost its charge.
Testing
1. If expansion valve inlet is cool to touch,
proceed 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").
d.) If expansion valve test indicates valve
operation is satisfactory, clean contact surface of
evaporator outlet pipe and temperature sensing
bulb, clamp bulb securely in contact with pipe.
Proceed with correction procedure (below).
2. If expansion valve inlet shows sweating or frost
proceed as follows:
a.) Discharge system.
b.) Disconnect inlet line at expansion valve,
remove and inspect screen.
c.)
Clean and replace screen, reconnect inlet line.
d.) Proceed with correction procedure (below).
3. If expansions valve test (step "1" preceding)
indicates valve is defective, proceed as follows:
a.) Discharge system.
b.) Replace expansion valve, then proceed with
correction procedure (below).
Correction
1. After cleaning expansion valve screen, or
replacing expansion valve if necessary, and
properly mounting temperature sensing bulb on
evaporator outlet pipe, proceed as follows:
a.) Evacuate system using vacuum pump.
b.) Charge system with NEW Refrigerant-12.
c.) Operate system and check performance.
N4-12