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SYMPTOM
Compressor and outdoor fan
will not start
Compressor will not start but condenser fan
runs
Three-phase scroll compressor (size 030-
060 units) may be a low pressure differential
Compressor cycles (other than normally
satisfying thermostat)
Compressor operates continuously
Excessive head pressure
SYMPTOM
Head pressure too low
Excessive suction pressure
Suction pressure too low
Compressor runs but outdoor fan does not
IFM does not run
IFM operation is intermittent
IFM–Indoor Fan Motor
TABLE 7—TROUBLESHOOTING CHART
CAUSE
Power Failure
Fuse blown or circuit breaker tripped
Defective thermostat, contactor, transformer,
control relay, defrost board, or high pressure or loss-
of-charge/low pressure switch
Insufficient line voltage
Incorrect or faulty wiring
Thermostat setting too high
Units have a 5-minute time delay
Faulty wiring or loose connections in compressor
circuit
Compressor motor burned out, seized, or
internal overload open
Defective run capacitor, overload, or PTC
(positive temperature coefficient) thermistor
One leg of 3-phase power dead
Low input voltage (20 percent low)
Scroll compressor is rotating in the wrong
direction
Refrigerant overcharge or undercharge
Defective compressor
Insufficient line voltage
Blocked outdoor coil
Defective run/start capacitor, overload or start
relay
Defective thermostat
Faulty outdoor-fan motor or capacitor
Damaged reversing valve
Restriction in refrigerant system
Dirty air filter
Unit undersized for load
Thermostat set too low
Low refrigerant charge
Frosted coil with incorrect defrost operation
Air in system
Outdoor coil dirty or restricted
Dirty air filter
Dirty indoor or outdoor coil
Refrigerant overcharged
Air in system
(Heat) Indoor air restricted or recirculating
Indoor or outdoor air restricted or air short-cycling
CAUSE
Low refrigerant charge
Restriction in liquid tube
(Heat) Outdoor coil frosted
(Cool) High Heat load
Reversing valve hung up or leaking internally
Refrigerant overcharged
(Cool) Dirty air filter
(Heat) Outdoor coil frosted
Low refrigerant charge
Metering device or low side restricted
(Cool) Insufficient coil airflow
(Cool) Temperature too low in conditioned area
(Cool) Outdoor ambient below 40°F
Filter-drier restricted
NC (normally closed) contacts on defrost board
open
Blower wheel not secured to shaft
Insufficient voltage at motor
Power connectors not properly sealed
Water dripping into motor
Connectors not firmly sealed
—26—
REMEDY
Call power company
Replace fuse or reset circuit breaker
Replace component
Determine cause and correct
Check wiring diagram and rewire correctly
Lower thermostat setting below room
temperature
DO NOT bypass this compressor time
delay–wait for 5 minutes until time-delay
relay is deenergized
Check wiring and repair or replace
Determine cause.
Replace compressor
Determine cause and replace
Replace fuse or reset circuit breaker. Determine
cause
Determine cause and correct
Correct the direction of rotation by reversing the
3-phase power leads to the unit
Recover refrigerant, evacuate system, and
recharge to capacities shown on nameplate
Replace and determine cause
Determine cause and correct
Determine cause and correct
Determine cause and replace
Replace thermostat
Replace
Determine cause and correct
Locate restriction and remove
Replace filter
Decrease load or increase unit size
Reset thermostat
Locate leak, repair, and recharge
Check defrost time settings
Reset as necessary
Check defrost temperature switch
Replace as necessary
Recover refrigerant, evacuate system,
and recharge
Clean coil or remove restriction
Replace filter
Clean coil
Recover excess refrigerant
Recover refrigerant, evacuate system,
and recharge
Determine cause and correct
Determine cause and correct
REMEDY
Check for leaks, repair and recharge
Remove restriction
Move timer on control board to 30 minutes
between defrost cycles
Check for source and eliminate
Replace valve
Recover excess refrigerant
Replace filter
Move timer on control board to 30 minutes
between defrost cycles
Check for leaks, repair and recharge
Remove source of restriction
Increase air quantity
Check filter–replace if necessary
Reset thermostat
Install low-ambient kit
Replace
Check condition of relay on board
Replace if necessary
Properly tighten blower wheel to shaft
Determine cause and correct
Connectors should snap easily; do not force
Verify proper drip loops in connector wires
Gently pull wires individually to be sure they are
crimped into the housing
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