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JOHNSON CONTROLS
133
FORM 150.63-NM6 (1020)
CONT’D
TROUBLESHOOTING (CONT’D)
3
PROBLEM
CAUSE
SOLUTION
“LOW SUCTION PRESSURE”
4. TXV defective.
4. Replace TXV.
FAULT (CONT’D)
5. Reduced flow of air through
5. Check CFM
the evaporator coil.
6. Defective suction pressure
6. Replace transducer/low
transducer/low pressure
pressure switch or faulty
switch or wiring.
wiring. Refer to “Service”
section for pressure/voltage
formula.
7. LLSV defective
7. Replace LLSV
“HIGH DISCHARGE
1. Condenser fans not operating
1. Check fan motor, fuses,
PRESSURE” FAULT
or operating backwards.
and contactors. Assure fan
blows air upward.
2. Too much refrigerant.
2. Remove refrigerant.
3. Air in refrigerant system.
3. Evacuate and recharge
system.
4. Defective discharge
4. Replace discharge pressure
pressure transducer.
transducer. Refer to Service
section for pressure/voltage
formula.
“MP / HPCO” FAULT
1. C
ompressor internal motor
1. Verify refrigerant charge is
protector (MP) open.
not low. Verify superheat
setting of °10 - 15°F (5.6° -
8.3°C). Verify correct com-
pressor rotation. Verify
compressor is not over
loaded.
2. External overload tripped.
2. Determine cause and reset.
3. HPCO switch open
3. See “High Press. Disch.”
Fault.
4. Defective HPCO switch
4. Replace HPCO switch
5. Defective CR relay
5. Replace relay
Summary of Contents for YCUL0045
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