42
DIAGNOSTICS
Service Analyzer Charts
THERMOSTATIC EXPANSION VALVES (cont.)
SYMPTOM
POSSIBLE CAUSE
REMEDY
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back upon start-up
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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 Elec-
trical 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
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Check for blocked distributor tubes.
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Ensure blower is moving proper air CFM.
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Superheat and
suction pressure
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hunting)
Expansion valve is oversized
Install correct TEV.
Sensing bulb is affected by liquid refrigerant or
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Relocate sensing bulb in another position around the
circumference of the suction line.
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circuits
Ensure sensing bulb is located properly.
Check for blocked distributor tubes.
Moisture freezing and partially blocking TEV
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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
