Do you feel like repairing your Mitsubishi air conditioner on your own or would you prefer to require a service engineer visit? The answer to this question to a large extent depends on the type of issue the appliance is experiencing. To find it out, consult the tables below. They contain explanations of the most common problems, as well as solutions that can make your air conditioner work again.
| State of Machine | Cause | Troubleshooting |
| It does not run. | Power failure. | Press the [ON/OFF] button after power restoration. |
| The power supply is turned OFF | Turn the power supply ON. | |
| The fuse in the power supply is gone. | Replace fuse. | |
| The earth leakage breaker is gone. | Put in the earth leakage breaker. | |
| Air flows out but it does not cool or heat enough. | Improper temperature adjustment. | After checking the set temperature. |
| The filter is filled with dust and dirt. | Clean up the filter. | |
| There are some obstacles at the air inlet and outlet of the units. | Remove. | |
| Windows and doors are open. | Close. | |
| Insufficient refrigerant charge. | Contact with your installing contractor. | |
| Cool or warm air does not come out. | The restart-preventing circuit is in operation for 3 minutes. | Wait for a while. (To protect the compressor, a 3-minute restart- preventing circuit is built into the unit. Therefore, there are occasions sometimes when the compressor does not start running immediately. There are cases when it does not run for as long as 3 minutes.) |
| Indoor unit operation was started anew during the heating and defrosting operation. (5 -10 HP only) | Wait for a while. (Heating operation starts after ending defrosting operation.) | |
| Fan runs but compressor do not run. | The set temperature of thermostat is excessively high for cooling, excessively low for heating. (PEH only) | For temperature control, decrease the set temperature at cooling. increase the set temperature at heating. (PEH only) |
| The room temperature is excessively low for cooling, excessively high for heating. (PEH only) | Can not be operated as it is out of temperature control range. | |
| Fan runs but stops immediately. | Air outlet and inlet are blocked. | Remove blocking matter. |
| Fogged white steam is discharged from the indoor unit. | When the indoor temperature and humidity are high, such a phenomenon is occasionally had at the beginning of system operation. | It is not a breakdown. Please use as it is. |
| Water or steam is discharged from the outdoor unit. | At cooling, water which places to cooling piping and piping connection part drops. When heating, water which places to the heat exchanger drops. (PEH only) | |
| On heating, the air flow stops although a set temperature is not reached. (PEH only) | Frost adheres to the outdoor coil when the temperature on the outside is low and humidity is high. This frost is melted. |
| Troubleshooting | Solution |
| Air conditioner does not heat or cool well. | ■ Clean the filter. (Airflow is reduced when the filter is dirty or clogged.) |
| ■ Check the temperature adjustment and adjust the set temperature. | |
| ■ Make sure that there is plenty of space around the outdoor unit. Is the indoor unit air intake or outlet blocked? | |
| ■ Has a door or window been left open? | |
| When heating operation starts, warm air does not blow from the indoor unit immediately. | ■ Warm air does not blow until the indoor unit has sufficiently warmed up. |
| During heating mode, the air conditioner stops before the set room temperature is reached. | ■ When the outdoor temperature is low and the humidity is high, frost may form on the outdoor unit. If this occurs, the outdoor unit performs a defrosting operation. Normal operation should begin after approximately 10 minutes. |
| When the airflow direction is changed, the vanes always move up and down past the set position before finally stopping at the position. | ■ When the airflow direction is changed, the vanes move to the set position after detecting the base position. |
| A flowing water sound or occasional hissing sound is heard. | ■ These sounds can be heard when refrigerant is flowing in the air conditioner or when the refrigerant flow is changing. |
| A cracking or creaking sound is heard. | ■ These sounds can be heard when parts rub against each due to expansion and contraction from temperature changes. |
| The room has an unpleasant odor. | ■ The indoor unit draws in air that contains gases produced from the walls, carpeting, and furniture as well as odors trapped in clothing, and then blows this air back into the room. |
| A white mist or vapor is emitted from the indoor unit. | ■ If the indoor temperature and the humidity are high, this condition may occur when operation starts. |
| ■ During defrosting mode, cool airflow may blow down and appear like a mist. | |
| Water or vapor is emitted from the outdoor unit. | ■ During cooling mode, water may form and drip from the cool pipes and joints. |
| ■ During heating mode, water may form and drip from the heat exchanger. | |
| ■ During defrosting mode, water on the heat exchanger evaporates and water vapor may be emitted. | |
| The operation indicator does not appear in the remote controller display. | ■ Turn on the power switch. “(§>” will appear in the remote controller display. |
| “IFST appears in the remote controller display. | ■ During central control, ‘Q” appears in the remote controller display and air conditioner operation cannot be started or stopped using the remote controller. |
| When restarting the air conditioner soon after stopping it, it does not operate even though the ON/OFF button is pressed. | ■ Wait approximately three minutes. (Operation has stopped to protect the air conditioner.) |
| Air conditioner operates without the ON/OFF button being pressed. | ■ Is the on timer set? Press the ON/OFF button to stop operation. |
| ■ Is the air conditioner connected to a central remote controller? Consult the concerned people who control the air conditioner. | |
| ■ Does “1ST appear in the remote controller display? Consult the concerned people who control the air conditioner. | |
| ■ Has the auto recovery feature from power failures been set? Press the ON/OFF button to stop operation. | |
| Air conditioner stops without the ON/OFF button being pressed. | ■ Is the off timer set? Press the ON/OFF button to restart operation. |
| ■ Is the air conditioner connected to a central remote controller? Consult the concerned people who control the air conditioner. | |
| ■ Does “|F3T appear in the remote controller display? Consult the concerned people who control the air conditioner. | |
| Remote controller timer operation cannot be set. | ■ Are timer settings invalid? If the timer can be set. ( weekly ). ( simple ). or Cauto off aooears in the remote controller display. |
| “PLEASE WAIT” appears in the remote controller display. | ■ The initial settings are being performed. Wait approximately 3 minutes. |
| An error code appears in the remote controller display. | ■ The protection devices have been operated to protect the air conditioner. |
| ■ Do not attempt to repair this equipment by yourself. Turn off the power switch immediately and consult your dealer. Be sure to provide the dealer with the model name and information that appeared in the remote controller display. | |
| Draining water or motor rotation sound is heard. | ■ When cooling operation stops, the drain pump operates and then stops. Wait approximately 3 minutes. |
| Cause | Symptoms | |
| One-to-one system | Group control | |
| (1) Wrong indoor-outdoor connections, or a reverse phase in the power line to the outdoor unit | • In cooling mode, indoor coil temperature code does not change. | • The same symptom as on the left appears when the master unit (the unit to which the remote controller is connected) is not correctly wired. |
| • The remote controller display temporarily shows “CENTRALLY CONTROLLED” when operation is started, but disappears soon afterward. (The same symptom appears if there is a short circuit in the remote controller wiring.) | • When any of the slave units are incorrectly wired, the blower will not run, or nine to ten minutes later, the system displays “P8” followed by the slave unit number. | |
| (2) Improper setting of the remote controller or the indoor unit address | • The remote controller display shows “CENTRALLY CONTROLLED”, but the switches fail to work. (On shipping, the remote controller and indoor unit are set to the address “0”. Accidental setting changes can cause this symptom.) | • The same symptom as on the left appears when the master unit or remote controller has a setting error. • If there are overlapping slave addresses, the system shows “P7” followed by the overlapping unit number. |
| (3) Wrong connections or a short circuit in the remote controller | • Nothing is displayed on the remote controller. | • The same as on the left |
| (4) In a two-remote controller system, no setting was made for the slave remote controller. (DIPSW® should be set to ON.) | • “P7” is shown sometimes. | |
| (5) In group control, connector CN40 is still connected in the slave units (No.1 and afterward). | • Nothing is displayed on the remote controller. |
| Unit conditions at service | Error code | Actions to be taken for service (summary) |
| The trouble is reoccurring. | Displayed | Judge what is wrong and take a corrective action according to ‘SELF-DIAGNOSIS ACTION TABLE’ (10-3). |
| Not displayed | Conduct troubleshooting and ascertain the cause of the trouble according to “TROUBLESHOOTING BY INFERIOR PHENOMENA ” (10-4). | |
| The problem is not reoccurring. | Logged | Consider the temporary defects such as the work of protection devices in the refrigerant circuit including compressor, poor connection of wiring, noise and etc. Re-check the symptom, and check the installation environment, refrigerant amount, weather when the trouble occurred, matters related to wiring and etc. |
| Reset error code logs and restart the unit after finishing service. | ||
| There is no abnormality in electrical component, controller board, remote controller and etc. | ||
| Not logged | Re-check the abnormal symptom. | |
| Conduct troubleshooting and ascertain the cause of the trouble according to ‘TROUBLESHOOTING BY INFERIOR PHENOMENA” (10-4). | ||
| Continue to operate unit for the time being if the cause is not ascertained. | ||
| There is no abnormality concering of parts such as electrical component, controller board, remote controller and etc. |
| Indoor unit display section | Description of trouble | Cause | Display (flashing) condition | |
| RUN light | TIMER light | |||
| 1 – time flash | ON | Indoor heat exchanger sensor error | • Broken heat exchanger sensor wire, poor connector connection • Indoor PCB is faulty | When a heat exchanger sensor wire disconnection is detected while operation is stopped. (If a temperature of-28°C or lower is detected for 15 seconds, it is judged that the wire is disconnected.) (Not displayed during operation.) |
| 2 – time flash | Room temperature sensor error | • Broken room temperature sensor wire, poor connector connection • Indoor PCB is faulty | ||
| 5 – time flash | Active filter voltage error | • Defective active filter | When the wrong voltage connected for the power supply. When the outdoor PCB is faulty’. | |
| 6 – time flash | Indoor fan motor error | • Defective fan motor, poor connector connection | When conditions for turning the indoor unit’s fan motor on exist during air conditioner operation, an indoor unit fan motor speed of 300 min’1 or lower is measured for 30 seconds or longer. (The air conditioner stops.) | |
| 7 – time flash | Refrigeration cycle system protective control | • Service valve is closed. • Refrigerant is insufficient | When refrigeration cycle sy stem protective control operates. | |
| Keeps flashing | 1 – time flash | Outdoor air temperature sensor error | • Broken outdoor air temp, sensor wire, poor connector connection • Outdoor PCB is faulty | -55^ or lower is detected for 5 seconds continuously 3 times within 40 minutes after initial detection of this anomalous temperature. Or -551^ or higher is detected for within 20 seconds after power ON. (The compressor is stopped.) |
| 2-time flash | Outdoor heat exchanger sensor error | • Broken heat exchanger sensor wire, poor connector connection • Outdoor PCB is faulty | ||
| 4-time flash | Discharge pipe sensor error | • Broken discharge pipe sensor wire, poor connector connection • Outdoor PCB is faulty | -25^ or lower is detected for 5 seconds continuously 3 times within 40 minutes after initial detection of this anomalous temperature. (The compressor is stopped.) | |
| ON | 1 – time flash | Current cut | • Compressor locking, open phase on compressor output, short circuit on power transistor, closed service valve | The inverter output current (compressor motor current) exceeds the set value during compressor start. (The air conditioner stops.) |
| 2-time flash | Trouble of outdoor unit | • Broken compressor wire • Compressor blockage | When there is an emergency’ stop caused by trouble in the outdoor unit, or the input current value is found to be lower than the set value. (The air conditioner stops.) | |
| 3-time flash | Current safe stop | • Overload operation • Overcharge • Compressor locking | When the compressor command speed is lower than the set value and the current safe has operated. (The compressor is stopped.) | |
| 4-time flash | Power transistor error | • Broken power transistor | When there is an emergency’ stop caused by trouble in the outdoor unit, or the input current value is found to be lower than the set value continuously for 3 minutes or longer. (The compressor is stopped.) | |
| 5-time flash | Over heat of compressor | • Gas shortage, defective discharge pipe sensor, closed service valve | When the value of the discharge pipe sensor exceeds the set value. (The air conditioner stops.) | |
| 6-time flash | Error of signal transmission | • Defective power supply, Broken signal wire, defective indoor/outdoor PCB | When there is no signal between the indoor PCB and outdoor PCB for 10 seconds or longer (when the power is turned on), or when there is no signal for 7 minute 35 seconds or longer (during operation) (The compressor is stopped). | |
| 7-time flash | Outdoor fan motor error | • Defective fan motor, poor connector connection | When the outdoor unit’s fan motor sped continues for 30 seconds or longer at 75 rpm or lower. (3 times) (The air conditioner stops.) | |
| Keeps flashing | Cooling high Pressure protection | • Overload operation, over charge • Broken outdoor heat exchange sensor wire • Service valve is closed. | When the value of the outdoor heat exchanger sensor exceeds the set value. | |
| 2 – time flash | 2-time flash | Rotor lock | • Defective compressor • Open phase on compressor • Defective outdoor PCB | If the compressor motor’s magnetic pole positions cannot be correctly detected when the compressor starts. (The air conditioner stops.) |