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9.0 DIAGNOSTICS & TROUBLESHOOTING
9.9 Service Analyzer Charts (cont.)
Diagnostics
COMPRESSOR OVERHEATING - HIGH DISCHARGE TEMP
SYMPTOM
POSSIBLE CAUSE
CHECK/REMEDY
High superheat
(greater than
15
o
F [8.3
o
C] at
coil)
Low Charge
Check system charge.
Verify suction thermistor operation (10k thermistor)
Replace thermistor.
Verify pressure transducer operation input and
output voltage
Replace thermistor and/or harness and/or control
board.
Faulty entering device, inadequate suction thermis
-
tor or pressure transducer operation
Restricted cap tube, EXV.
Foreign matter stopping flow.
High internal load
Hot air (attic) entering return.
Heat source on; miswired or faulty control.
Restriction in liquid line
Drier plugged.
Line kinked.
Low head pressure
Low charge.
Operating in low ambient temperatures.
Suction or liquid line subjected to high heat source
Hot attic.
Hot water line.
Low line voltage
Loose wire connections
Check wiring.
Power company problems, transformer
Report problem.
Undersized wire feeding unit
Correct and complete diagnosis.
High line voltage
Power company problem
Report problem.
High head
pressure
Overcharge
Check system charge.
Dirty head pump coil
Clean coil.
Faulty or wrong size outdoor fan motor
Replace fan motor.
Faulty fan blade or wrong rotation
Replace fan blade.
Replace with correct rotation motor.
Recirculation of air
Correct installation.
Additional heat source
Check for dryer vent near unit.
Check for recirculation from other equipment.
Noncondensibles
Recover refrigerant. Evacuate and recharge system.
Equipment not matched
Correct mismatch.
Short cycling of
compressor
Cycling or faulty pressure control
Check pressure and address cause of high or low
pressure. Replace pressure control if faulty.
Loose wiring
Check unit wiring.
Thermostat
Located in supply air stream.
Differential setting too close.
Customer misuse.
EXV restricted or not functioning properly.
Internal foreign matter.
Pressure transducer failure.
Suction thermistor failure.
EXV control failure
EXV coil failure
Distributor tube/tubes restricted
Distributor tube
Restricted with foreign matter
Kinked
Inside diameter reduced from previous compressor
failure
