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9.0 DIAGNOSTICS & TROUBLESHOOTING
9.9 Service Analyzer Charts (cont.)
Diagnostics
ELECTRONIC EXPANSION VALVES (cont.)
SYMPTOM
POSSIBLE CAUSE
REMEDY
Valve feeds too much
refrigerant, with low
superheat, with low
superheat and
higher than normal
suction pressure.
Moisture causing valve to stick open
Recover refrigerant, replace filter-drier, evacuate system, and
recharge.
Dirt or foreign material causing valve to stick open
Recover refrigerant, replace filter-drier, remove EXV and purge
with nitrogen, replace filter drier, and recharge.
Oversized EXV
Install correct EXV.
Incorrect suction thermistor location
Install suction thermistor with the provided stainless steel strap
and an additional zip tie between the 10:00 and 2:00 position on
suction line, with insulation.
Low superheat adjustment
Charge the superheat offset dip switches on indoor coil EXV
control to increase superheat.
Incorrectly sensing suction line temperature
Verify suction thermistor resistance is correct and properly
attached and insulated to the suction line.
Suction thermistor incorrectly calibrated
Replace suction thermistor assembly.
Suction pressure measured incorrectly
After verifying lack of connectivity, replace the pressure transducer
or harness.
If harness has a short, replace harness.
If gauge pressure measurement and the converted voltage
readings at the control are different replace pressure transducer.
If gauge pressure measurement and the converted voltage
readings at the control are the same, replace the control.
Compressor flood
back upon start-up
Refrigerant drainage from flooded evaporator
Install trap riser to top of the evaporator coil.
Inoperable stator heat
Verify compressor thermistor (OST). Replace if needed.