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9.13 Troubleshooting Tips
Diagnostics
9.0 DIAGNOSTICS & TROUBLESHOOTING
COOLING MODE
TROUBLESHOOTING TIPS
SYSTEM
PROBLEM
INDICATORS
DISCHARGE
PRESSURE
SUCTION
PRESSURE
SUPERHEAT
Normal: 5°–15°F
[2.8° – 8.3°C]
SUBCOOLING
Normal: See
Charging Chart
Overcharge
High
Low
High
High
Low
Low
High
High
High
Low
High
High
Undercharge
Low
Low
Low
Liquid Restriction
(Filter Drier)
Low
Low
High
Low
Low
Low
Dirty Outdoor Coil
High
High
Low
Low Outdoor
Ambient Temperature
Low
Low
High
Compressor
Low
High
High
Bad Indoor Suction
Pressure Transducer or
Faulty Measurement
Low
Low
High
Poorly Insulated
Indoor Vapor Line
Thermistor or Bad
Thermistor
High
High
Low
HEATING MODE
TROUBLESHOOTING TIPS
SYSTEM
PROBLEM
INDICATORS
DISCHARGE
PRESSURE
SUCTION
PRESSURE
SUPERHEAT
Normal: 5°–15°F
[2.8° – 8.3°C]
SUBCOOLING
Normal: See
Charging Chart
Overcharge
High
High
OK
High
Undercharge
Low
Low
OK or High
Low
Liquid Restriction
Low
Low
High
High
Low
Low
Low
Low
Dirty Indoor Coil
High
High
Low
Low
Low Indoor Ambient
Temperature
Low
Low
OK
High
Compressor
Low
High
High
High
Low
Low
High
High
High
High
Low
Low
Bad Outdoor Suction
Pressure Transducer or
Faulty Measurement
Poorly Insulated
Outdoor Vapor Line
Thermistor or Bad
Thermistor
(Filter Drier)