Toshiba MMU-AP0121MH, MMU-AP0181MH, MMU-AP0151MH H06 Low-pressure protective operation

Check code name Check code name Cause of operation

[H04]	Compressor 1 case thermo operation 1. Case thermo circuit error
[H14]	Compressor 2 case thermo operation	2.	I/F P.C. board error
		3.	Service valve closed
		4.	Outdoor PMV clogging
		5.	SV4 valve leak, Coil misinstallation
		6.	4-way valve error
		7.	Compressor error
		8.	Refrigerant shortage

Check code name Check code name Cause of operation

[H06]	Low-pressure protective operation	1. Service valve close
		2.	Ps sensor error
		3.	SV2, SV4 circuit error
		4.	Miscabling of communication between
			indoor and outdoor
		5.	Indoor/outdoor fan and condenser error
		6.	Indoor/outdoor PMV clogging
		7.	Indoor/outdoor heat exchanger clogging
		8.	Refrigerant shortage

Is case thermo circuit normal?

1.Connector connection

2.Wiring

3.I/F P.C. board (Note 1)

YES

Are service valves of

gas pipe and liquid pipe of outdoor unit fully opened?

NO

(Note 1)

1.Case thermo is usually closed.

2.Operation temperature of case thermo is 120˚C.

NO

Repair case thermo circuit.

Open service valves fully.

Are service valves of gas and

liquid pipe of outdoor unit fully opened?

YES

Are characteristics of low-pressure sensor normal?

YES

NO

Open service valves fully.

NO

Exchange low-pressure sensor.

1 Pressure by pressure gauge (Check joint)

2Pressure display on 7-segment display

3Output voltage of I/F P.C. board

If 1 and 2, 3 are different, an error of pressure sensor error is considered. If 2 and 3 are different, check I/F P.C. board.

74

YES

Are outdoor PMV1/2/3 normal? 1. Connector connection

2. Wiring	3. Coil
4. Valve body	5. I/F P.C. board
	YES

Operation starts.

Are SV41 and SV42

Valve circuits normal?

1.Misinstallation installation and connector connection of SV41 and SV42

2.Leakage from SV41, 42 circuit

YES

Does not refrigerant

bypass from discharge of

suction through 4-way valve?

NO

Is not refrigerant bypassed from discharge to suction?

NO

Is compressor normal? (Note 2)

NO

Connector CN300, 301, White

NO

SV4 valve: Connector CN311, Blue

YES

YES

NO

Repair outdoor PMV.

Correct SV4, SV5, SV11

valve circuits.

Check 4-way valve.

Check piping.

Compressor error

Are SV2 and SV4 circuits normal?

NO

Correct SV2 and SV4 circuits.

Check miscabling, misinstallation and

YES

connector connection.

Is there no mispiping of discharge gas

YES

Correct piping.

and suction gas main pipes?

NO

Is not indoor unit with different circuit connected?

YES

Correct cabling.

(Check with miscabling check

NO

function of outdoor unit.)

Is flow selector normal?

NO

Check flow selector.

YES

In cooling season, go to (A), In heating season, go to (B)

(A) Cooling

Are following items concerned

Does indoor fan normally

NO

to indoor fan motor normal?

NO

1. Connector connection

Repair faulty parts.

operate in cooling season?

2. Condenser

YES

3. Motor

4. Fan

YES

Cleaning

Is there clogging of indoor

YES

Check indoor P.C. board.

air filter or heat exchanger?

NO

NO

Is connector connection

NO

Failure Replace

Is indoor PMV normal?

or coil normal?

Repair faulty parts.

YES

YES

YES

Refrigerant shortage or

Is there clogging on whole valve?

Replace PMV body.

clogging or pipe deformed

NO

(B) Heating

NO

Is outdoor fan normally

NO

Is indoor fan system normal?

Check outdoor

YES	(Note 2) Check the following items mainly.
	1. Existence of abnormal sound and abnormal vibration during operation at start time

operated in heating season?	• Fan crack	I/F P.C. board.
	• Fan coming-off	Failure Replace

2.	Abnormal overheat of case during operation or stop (Never touch with hands.)
3.	Current of compressor lead during operation or starting (No rapid current change)
	YES
Is flow selector unit normal?		Check flow selector unit.

Cleaning

YES

YES

Is there clogging of

outdoor heat exchanger?

YES

Repair faulty parts.

NO

Refrigerant shortage,

NO

Is outdoor PMV normal?

YES

NO

clogging, pipe breakage (After checking there is no slogging or pipe breakage, charge refrigerant again.)

Refrigerant shortage,

clogging, pipe deformed