Table 7—Troubleshooting Chart
SYMPTOM CAUSE REMEDY
Compressor and outdoor fan
will not start
Power Failure Call power company
Fuse blown or circuit breaker tripped Replace fuse or reset circuit breaker
Defective thermostat, contactor, transformer,
control relay, defrost board, or high pressure or loss-
of-charge/low pressure switch
Replace component
Insufficient line voltage Determine cause and correct
Incorrect or faulty wiring Check wiring diagram and rewire correctly
Thermostat setting too high
Lower thermostat setting below room
temperature
Units have a 5-minute time delay
DO NOT bypass this compressor time
delay–wait for 5 minutes until time-delay
relay is deenergized
Compressor will not start but condenser fan
runs
Faulty wiring or loose connections in compressor
circuit
Check wiring and repair or replace
Compressor motor burned out, seized, or
internal overload open
Determine cause.
Replace compressor
Defective run capacitor, overload, or PTC
(positive temperature coefficient) thermistor
Determine cause and replace
One leg of 3-phase power dead
Replace fuse or reset circuit breaker. Determine
cause
Low input voltage (20 percent low) Determine cause and correct
Three-phase scroll compressor (size 030-
060 units) may be a low pressure differential
Scroll compressor is rotating in the wrong
direction
Correct the direction of rotation by reversing the
3-phase power leads to the unit
Compressor cycles (other than normally
satisfying thermostat)
Refrigerant overcharge or undercharge
Recover refrigerant, evacuate system, and
recharge to capacities shown on nameplate
Defective compressor Replace and determine cause
Insufficient line voltage Determine cause and correct
Blocked outdoor coil Determine cause and correct
Defective run/start capacitor, overload or start
relay
Determine cause and replace
Defective thermostat Replace thermostat
Faulty outdoor-fan motor or capacitor Replace
Damaged reversing valve Determine cause and correct
Restriction in refrigerant system Locate restriction and remove
Compressor operates continuously
Dirty air filter Replace filter
Unit undersized for load Decrease load or increase unit size
Thermostat set too low Reset thermostat
Low refrigerant charge Locate leak, repair, and recharge
Frosted coil with incorrect defrost operation
Check defrost time settings
Reset as necessary
Check defrost temperature switch
Replace as necessary
Air in system
Recover refrigerant, evacuate system,
and recharge
Outdoor coil dirty or restricted Clean coil or remove restriction
Excessive head pressure
Dirty air filter Replace filter
Dirty indoor or outdoor coil Clean coil
Refrigerant overcharged Recover excess refrigerant
Air in system
Recover refrigerant, evacuate system,
and recharge
(Heat) Indoor air restricted or recirculating Determine cause and correct
Indoor or outdoor air restricted or air short-cycling Determine cause and correct
(Continued next page)
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