Koolaire STH045 8/15 Technician's Handbook page 98

NOTE: A head pressure control valve that will not
bypass, will function properly with condenser air
temperatures of approximately 70°F (21°C) or above.
When the temperature drops below 70°F (21°C), the
head pressure control valve fails to bypass and the ice
machine malfunctions. Lower ambient conditions can
be simulated by rinsing the condenser with cool water
during the freeze cycle.
Condition
Discharge Pressure - High
Liquid Line Temperature -
Discharge Pressure - Low
Liquid Line Temperature -
Cold
Discharge Pressure - Low
Liquid Line Temperature -
98
Hot
Hot
Probable
Cause
Valve stuck in
bypass
Valve not
bypassing
Ice Machine
Low on
Charge
Part Number STH045 8/15
Corrective
Measure
Replace
valve
Replace
valve
Refrigerant
Charge
Verification