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Table 12—Troubleshooting—Cooling and Heating
SYMPTOM CAUSE REMEDY
Compressor and outdoor fan will not start.
Power Failure Call power company
Loss of Charge
Switch open
Evaluate unit for possible refrigerant leak
Fuse blown or circuit breaker tripped Replace fuse or reset circuit breaker
Defective thermostat, contractor, transformer, or
control relay
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 tempera-
ture
Compressor will not start but outdoor 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/start capacitor, overload, start relay Determine cause and replace
Low input voltage
(20 percent low)
Determine cause and correct
Compressor cycles
(other than normally satisfying thermostat).
Refrigerant overcharge or undercharge
Recover refrigerant, evacuate system, and re-
charge to capacities shown on nameplate
Loss of Charge
Switch open
Evaluate unit for possible refrigerant leak
Defective compressor Replace and determine cause
Insufficient line voltage Determine cause and correct
Blocked outdoor coil (cooling) 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
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
Leaking valves in compressor Replace compressor
Frosted outdoor coil with incorrect
defrost operation (heating)
Check defrost time settings. Reset as necessary.
Check defrost temperature switch. Replace as necessary.
Air in refrigerant system
Recover refrigerant, evacuate system, and re-
charge
outdoor coil dirty or restricted Clean coil or remove restriction
Excessive head pressure.
Dirty air filter Replace filter
Dirty outdoor coil Clean coil
Refrigerant overcharged Recover excess refrigerant
Air in refrigerant system
Recover refrigerant, evacuate system, and re-
charge
Outdoor or indoor air restricted
or air is recirculating
Determine cause and correct
Head pressure too low.
Low refrigerant charge Check for leaks, repair and recharge
Compressor valves leaking Replace compressor
Restriction in liquid tube Remove restriction
Excessive suction pressure.
High heat load Check for source and eliminate
Compressor valves leaking Replace compressor
Refrigerant overcharged Recover excess refrigerant
Suction pressure too low.
Dirty air filter (cooling) Replace Filter
Low refrigerant charge Check for leaks, repair, and recharge
Metering device or low side restricted Remove source of restriction
Insufficient indoor airflow (cooling)
Increase air quantity
Check filter- replace if necessary
Temperature too low in conditioned area (cooling) Reset thermostat
Outdoor ambient below 40°F (cooling) Install low-ambient kit
Field-installed filter-drier restricted Replace
Compressor runs but
outdoor fan does not.
Normally closed contacts on
defrost board open
Check condition of relay on board.
Replace board if necessary.
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