Sanyo KHX1252, UHX2452, UHX0752, UHX1252, UHX3652, UHX1852, THX2452, THX1252 P04 Alarm Alarm code

Trouble Diagnosis

3. W-2WAY ECO-i Alarm Codes

P04 Alarm

Alarm code	P04
Alarm meaning	High-pressure switch activated.
Alarm conditions	When the electrical circuit of the high-pressure switch is activated, then depending on the
	pressure, the terminals may be short-circuited. If the pressure is 464 psi or higher, the terminals
	will be short-circuited. When they have been short-circuited, they remain short-circuited until the
	pressure decreases to 360 psi.
Probable cause	(1)	The check valve installed on the compressor discharge-side tubing has malfunctioned.
	(2)	The service valve is closed.
	(3)	The outdoor unit heat exchanger became clogged during cooling operation.
	(4)	An air short circuit occurred in the outdoor unit during cooling operation.
	(5)	The outdoor unit fan malfunctioned during cooling operation.
	(6)	The indoor unit air filter became clogged during heating operation.
	(7)	An air short circuit occurred in the indoor unit during heating operation.
	(8)	The indoor fan failed during heating operation.
	(9)	The refrigerant circuit has become clogged.
	(10)	The mechanical valve failed.
	(11)	The solenoid valve kit failed.
	(12)	Refrigerant overcharge has occurred.
	(13)	The high-pressure switch failed.
Check	(1)	Check that the high-pressure switch connector is connected securely.
	(2)	If it is connected securely, then connect a pressure gauge to the high-pressure outlet and
		monitor the high pressure while operating the system. Check the pressure at the time when
		the high-pressure switch operates. If the pressure is less than 551 psi then it is possible
		that the check valve has failed.
	The following concern cases in which the pressure is actually too high.
	(3)	If the operation is cooling operation, check that the outdoor heat exchanger has not become
		clogged or blocked. Remove any objects that impede the flow of air.
	(4)	If the operation is cooling operation, check that an air short circuit has not occurred at the
		outdoor unit. The status is OK as long as the temperature in the area around the outdoor
		unit does not become abnormally high during operation.
	(5)	If the operation is cooling operation, check that the outdoor unit fan has not failed. Check that
		the screws which fasten the fan have not become loose. Check that the fan connector has
		been securely inserted into the outdoor unit PCB.
	(6)	If the operation is heating operation, check that the indoor unit air filter has not become
		clogged. If it is clogged, clean it.
	(7)	If the operation is heating operation, check that an air short circuit has not occurred at the
		indoor unit. The status is OK as long as the temperature in the area around the indoor unit
		air intake does not become abnormally high during operation.
	(8)	If the operation is heating operation, check that the indoor unit fan has not failed.
	(9)	Check that the refrigerant circuit has not become clogged. Check that all the service valves
		are fully opened. Check that the welded connections are not clogged.
	(10)	Check that the mechanical valves have not failed. Check whether or not mechanical valve 3
		makes a grinding sound when the power is reset. At the indoor unit, the mechanical valve is
		located at a position where it is difficult to hear, so this check should be made electronically.
		Check that 4 V is being output to the mechanical valve connector pin on the PCB. Also check
		that the mechanical valve coil winding resistance is several tens of Ohms.
	(11)	Check that the solenoid valve kit has not failed. Removing the coil when the valve is ON should
		produce a click sound. Removing the coil when the valve is OFF should produce no sound.
	(12)	Check that refrigerant overcharge has not occurred. If the sub-cool temperature at the
		condenser discharge is 59°F (15°C) or higher, overcharge has occurred.
Correction	Replace the failed part and correct the amount of refrigerant charge.
Example	—
Notes	—

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