Carrier WeatherMaster 50HCQA04, Service And Maintenance Instructions, Page: 20 / 98

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Table 6 –
Heating and Cooling Troubleshooting
PROBLEM 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. Determine root cause.
Defective thermostat, contactor, transformer,
control relay, or capacitor.
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.
High pressure switch tripped. See problem ‘‘Excessive head pressure.’’
Low pressure switch tripped. Check system for leaks. Repair as necessary.
Freeze-up protection thermostat tripped. See problem ‘‘Suction pressure too low.’’
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 or allow enough time for
internal overload to cool and reset.
Defective run/start capacitor, overload, start
relay.
Determine cause and replace compressor.
One leg of 3-phase power dead. Replace fuse or reset circuit breaker. Determine cause.
Compressor Cycles
(Other Than
Normally Satisfying
Thermostat).
Refrigerant overcharge or undercharge. Recover refrigerant, evacuate system, and recharge to nameplate.
Defective compressor. Replace and determine cause.
Insufficient line voltage. Determine cause and correct.
Blocked outdoor coil or dirty air filter. Determine cause and correct.
Defective run/start capacitor, overload, or start
relay.
Determine cause and replace.
Defective thermostat. Replace thermostat.
Faulty outdoor-fan (cooling) or indoor-fan
(heating) 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 (cooling). Reset thermostat.
Low refrigerant charge. Locate leak; repair and recharge.
Air in system. Recover refrigerant, evacuate system, and recharge.
Outdoor coil dirty or restricted. Clean coil or remove restriction.
Compressor Makes
Excessive Noise.
Compressor rotating in the wrong direction. Reverse the 3-phase power leads as described in
Start-Up.
Excessive Head
Pressure.
Dirty outside air or return air filter (heating). Replace filter.
Dirty outdoor coil (cooling). Clean coil.
Refrigerant overcharged. Recover excess refrigerant.
Air in system. Recover refrigerant, evacuate system, and recharge.
Condensing air restricted or air short-cycling. Determine cause and correct.
Head Pressure
Too Low.
Low refrigerant charge. Check for leaks; repair and recharge.
Compressor scroll plates defective. Replace compressor.
Restriction in liquid tube. Remove restriction.
Excessive Suction
Pressure.
High heat load. Check for source and eliminate.
Compressor scroll plates defective. Replace compressor.
Refrigerant overcharged. Recover excess refrigerant.
Suction Pressure
Too Low.
Dirty air filter (cooling). Replace filter.
Dirty or heavily iced outdoor coil (heating). Clean outdoor coil. Check defrost cycle operation.
Low refrigerant charge. Check for leaks; repair and recharge.
Metering device or low side restricted. Remove source of restriction.
Insufficient indoor airflow (cooling mode). Increase air quantity. Check filter and replace if necessary.
Temperature too low in conditioned area. Reset thermostat.
Field-installed filter drier restricted. Replace.
Outdoor ambient below 25
_
F (cooling). Install low-ambient kit.
Outdoor fan motor(s) not operating (heating). Check fan motor operation.