Maintenance
SS-SVX004C-EN
25
Noisy Compressor
Expansion valve stuck in open position
(abnormally cold suction line).
Check operation of the expansion valve and
superheat.
Worn or scarred compressor bearings.
Replace compressor.
Broken compressor valve (compressor
knocking, suction pressure rises faster than 2 lb/
min after shutdown).
Replace compressor.
Liquid slugging.
•
Ensure expansion valve is not stuck in open
position.
•
System overcharged. Reclaim excess
refrigerant.
Scroll compressor not properly phased.
Phase correctly at main power source. Do not
rewire compressor.
Blower Fails to Start
Power failure.
Check main voltage power source input cable.
Control transformer circuit breaker tripped.
Check for short circuit or ground fault; if none,
reset circuit breaker.
Defective contactor.
Repair or replace.
Motor starter protector tripped.
Reset motor starter protector and check
amperage of motor. Compare to setting of motor
protector and adjust FLA.
Head Pressure Too High
Low condensing unit airflow (indicated by
excessive warm air leaving the condensing unit
fan).
Open air passages. Clean coil. Check condensing
unit fan(s).
Air or other non-condensible gas in system.
Reclaim system and recharge. Install a new drier
strainer.
Overcharge of refrigerant.
Reclaim excess refrigerant from system.
Condensing unit fan not on.
•
Check main voltage power source to the
unit.
•
Check fan motor starter protector,
contactor, fan cycling switch or fan speed
controller.
Suction Pressure too Low
Expansion valve not opening fully (indicated by
abnormally cold suction line).
Open air passages. Clean coil. Check condensing
unit fan(s).
Low charge, flash gas in liquid line (indicated by
high superheat, low sub-cooling temperature
and low suction pressure).
Reclaim system and recharge. Install a new drier
strainer.
Clogged drier/strainer (feels cool to the touch). Reclaim excess refrigerant from system.
Obstructed expansion valve (indicated by loss of
capacity).
•
Check main voltage power source to the
unit.
•
Check fan motor starter protector,
contactor, fan cycling switch or fan speed
controller.
Compressor Fails to Start
Temperature setpoint too high.
Adjust to desired temperature.
Compressor internal overload protector is open. Check compressor for short circuit or ground.
Complete loss of refrigerant charge (low
pressure safety switch).
Locate and repair leak. Recharge system.
Condensing unit pressure too high (high
pressure safety switch).
Check condensing unit for obstructions. Re-set
high pressure switch.
Minimum off time has not expired.
Wait for time to expire.
System Short of Capacity
Low refrigerant (indicated by bubbles in sight
glass).
Check for leaks. Repair and recharge system.
Expansion valve stuck or obstructed (short
cycling or continuous running).
Remove valve and clear obstruction or replace
valve.
Reduced airflow.
Check belt tension, filters and clear evaporator
coil of debris.
Symptom
Probable Cause
Recommendation
