52
DIAGNOSTICS
Service Analyzer Charts
THERMOSTATIC EXPANSION VALVES (cont.)
SYMPTOM POSSIBLE CAUSE REMEDY
Compressor fl ood
back upon start-up
Refrigerant drainage from fl ooded evaporator Install trap riser to the top of the evaporator coil.
Inoperable crankcase heater or crankcase heater
needed
Replace or add crankcase heater.
Any of the causes listed under symptoms of
Electrical problems on page 45
Any of the solutions listed under solutions of Electrical
problems on page 45
Superheat is low to
normal with low
suction pressure
Unequal evaporator circuit loading Ensure airfl ow is equally distributed through evaporator.
Check for blocked distributor tubes.
Low load or airfl ow entering evaporator coil Ensure blower is moving proper air CFM.
Remove/Correct any airfl ow restriction.
Superheat and
suction pressure
fl uctuate (valve is
hunting)
Expansion valve is oversized Install correct TEV.
Sensing bulb is aff ected by liquid refrigerant or
refrigerant oil fl owing through suction line
Relocate sensing bulb in another position around the
circumference of the suction line.
Unequal refrigerant fl ow through evaporator
circuits
Ensure sensing bulb is located properly.
Check for blocked distributor tubes.
Moisture freezing and partially blocking TEV Recover refrigerant, change fi lter-drier, evacuate system,
and recharge.
Valve does not
regulate at all
External equalizer line not connected or line
plugged
Connect equalizer line in proper location, or remove any
blockage.
Sensing bulb lost its operating charge Replace TEV.
Valve body damaged during soldering or by
improper installation
Replace TEV.
Diagnostics
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