Carrier 38AUQ appendix Troubleshooting

TROUBLESHOOTING

PROBLEM	CAUSE	REMEDY
Compressor and	Power failure.	Call power company.
Outdoor Fan
	Fuse blown or circuit breaker tripped.	Replace fuse or reset circuit breaker. Determine root cause.
Will Not Start.
	Defective thermostat, contactor, transformer,	Replace component.
	control relay, or capacitor.
	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	Faulty wiring or loose connections in compressor	Check wiring and repair or replace.
Start But Outdoor	circuit.
Fan Runs.
	Compressor motor burned out, seized, or	Determine cause. Replace compressor or allow enough time for
	internal overload open.	internal overload to cool and reset.
	Defective run/start capacitor, overload, start	Determine cause and replace compressor.
	relay.
	One leg of 3-phase power dead.	Replace fuse or reset circuit breaker. Determine cause.
Compressor Cycles	Refrigerant overcharge or undercharge.	Recover refrigerant, evacuate system, and recharge to nameplate.
(Other Than
	Defective compressor.	Replace and determine cause.
Normally Satisfying
Thermostat).	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	Determine cause and replace.
	relay.
	Defective thermostat.	Replace thermostat.
	Faulty outdoor-fan (cooling) or indoor-fan	Replace.
	(heating) motor or capacitor.
	Restriction in refrigerant system.	Locate restriction and remove.
Compressor Operates	Dirty air filter.	Replace filter.
Continuously.
	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	Compressor rotating in the wrong direction.	Reverse the 3-phase power leads as described in
Excessive Noise.		Start-Up.
Excessive Head	Dirty outside air or return air filter (heating).	Replace filter.
Pressure.
	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	Low refrigerant charge.	Check for leaks; repair and recharge.
Too Low.
	Compressor scroll plates defective.	Replace compressor.
	Restriction in liquid tube.	Remove restriction.
Excessive Suction	High heat load.	Check for source and eliminate.
Pressure.
	Compressor scroll plates defective.	Replace compressor.
	Refrigerant overcharged.	Recover excess refrigerant.
Suction Pressure	Dirty air filter (cooling).	Replace filter.
Too Low.
	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.

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