The lists of issues which may lead to your Mitsubishi heat pump not working are displayed on the page below. There are several different modifications of Mitsubishi heat pumps and their possible breakdowns described.
For each of the models you can find a separate table with detailed description of problems which may cause heat pump not cooling or heat pump fan not spinning. For each symptom or error code there are some recommendations, remedies or necessary actions. For example, you may check the power supply or inspect some other functions.
If the heat pump needs serious repair or an action which you do not know how to do, care for your safety and call the specialists.
Mitsubishi ecodan EHPT20X-YM9C Heat Pump Troubleshooting
| POWER lamp Upper lamp | Abnormal point (Failure mode) | Condition |
|---|---|---|
| Not lighted | Normal | — |
| 1-time flash every 0.5-second | Room temperature thermistor | The room temperature thermistor short or open circuit is detected every 8 seconds during operation. |
| 2-time flash 2.5-second OFF | Indoor coil thermistor | The indoor coil thermistor short or open circuit is detected every 8 seconds during operation. |
| 3-time flash 2.5-second OFF | Serial signal | The serial signal from outdoor unit is not received for a maximum of 6 minutes. |
| 11-time flash 2.5-second OFF | Indoor fan motor | The rotational frequency feedback signal is not emitted for 12 seconds after the indoor fan motor is operated. |
| 12-time flash 2.5-second OFF | Indoor control system | It cannot properly read data in the nonvolatile memory of the indoor electronic control RC board. |
Mitsubishi EHSC Series Heat Pump Troubleshooting
| Display | Contents to be inspected (During operation) |
|---|---|
| U1 | Abnormal high pressure (63H operated) |
| U2 | Abnormal high discharging temperature and shell thermistor, shortage of refrigerant |
| U3 | Open/short circuit of discharging thermistor(TH4) and shell thermistor(TH32) |
| U4 | Open/short of outdoor unit thermistors(TH3, TH6, TH7 and TH8) |
| U5 | Abnormal temperature of heat sink |
| U6 | Abnormality of power module |
| U7 | Abnormality of superheat due to low discharge temperature |
| U8 | Abnormality in outdoor fan motor |
| Ud | Overheat protection |
| UF | Compressor overcurrent interruption (When Comp, locked) |
| UH | Current sensor error |
| UL | Abnormal low pressure |
| UP | Compressor overcurrent interruption |
| P1-P8 | Abnormality of indoor units |
| A0-A7 | Communication error of M-NET system |
Mitsubishi Mr. Slim Heat Pump Troubleshooting
| Display | Contents to be inspected (When power is turned on) |
|---|---|
| F5 | 63H connector(yellow) is open. |
| E8 | Indoor/outdoor communication error (Signal receiving error) (Outdoor unit) |
| E9 | Indoor/outdoor communication error (Transmitting error) (Outdoor unit) |
| EA | Misfiring of indoor/outdoor unit connecting wire, excessive number of indoor units (4 units or more) |
| Eb | Misfiring of indoor/outdoor unit connecting wire(converse wiring or disconnection) |
| EC | Startup time over |
| E0-E7 | Communication error except for outdoor unit |
Mitsubishi PQRY-P144YSLMU-A Heat Pump Troubleshooting
| Beeper sounds/OPERATION INDICATOR lamp flashes (Number of times) | Check code | Symptom |
|---|---|---|
| 1 | P1 | Intake sensor error |
| 2 | P2 | Pipe (TH2) sensor error |
| P9 | Pipe (TH5) sensor error | |
| 3 | E6.E7 | Indoor/outdoor unit communication error |
| 4 | P4 | Drain sensor error/Float switch connector (CN4F) open |
| 5 | P5 | Drain pump error |
| PA | Forced compressor stop (due to water leakage abnormality) | |
| 6 | P6 | Freezing/Overheating protection operation |
| 7 | EE | Communication error between indoor and outdoor units |
| 8 | P8 | Pipe temperature error |
| 9 | E4, E5 | Remote controller signal receiving error |
| 10 | - | - |
| 11 | - | - |
| 12 | Fb | Indoor unit control system error (memory error, etc.) |
| - | EO, E3 | Remote controller transmission error |
| - | El, E2 | Remote controller control board error |
Mitsubishi PUHZ-HW140VHA2-BS Heat Pump Troubleshooting
| Beeper sounds/OPERATION INDICATOR lamp flashes (Number of times) | Check code | Symptom |
|---|---|---|
| 1 | E9 | Indoor/outdoor unit communication error (Transmitting error) (Outdoor unit) |
| 2 | UP | Compressor overcurrent interruption |
| 3 | U3.U4 | Open/short of outdoor unit thermistors |
| 4 | UF | Compressor overcurrent interruption (When compressor locked) |
| 5 | U2 | Abnormal high discharging temperature/insufficient refrigerant |
| 6 | U1,Ud | Abnormal high pressure (63H operated)/Overheating protection operation |
| 7 | U5 | Abnormal temperature of heatsink |
| 8 | U8 | Outdoor unit fan protection stop |
| 9 | U6 | Compressor overcurrent interruption/Abnormal of power module |
| 10 | U7 | Abnormality of superheat due to low discharge temperature |
| 11 | U9.UH | Abnormality such as overvoltage or voltage shortage and abnormal synchronous signal to main circuit/Current sensor error |
| 12 | - | - |
| 13 | - | - |
| 14 | Others | Other errors |
Mitsubishi QAHV Heat Pump Troubleshooting
| Error code | Inspected content |
|---|---|
| U4 | Open/short of outdoor unit thermistor (TH3/TH6/TH7/TH8) |
| E8 | Indoor/outdoor unit communication error |
| • Signal receiving error (Outdoor unit) | |
| E9 | Indoor/outdoor unit communication error |
| • Transmitting error (Indoor unit) | |
| EO - E7 | Communication error other than outdoor unit |
| Ed | Communication error between outdoor controller board and M-NET board (Serial communication error) |
Mitsubishi SEZ-KD09NA4.TH Heat Pump Troubleshooting
| Phenomena | Factor | Countermeasure |
|---|---|---|
| 1. Remote controller display does not work. | ODC12V is not supplied to remote controller. (Power supply display (•) is not indicated on LCD.) (DDC12-15V is supplied to remote controller, however, no display is indicated. | Check LED2 on indoor controller board. |
| • ‘PLEASE WAIT is not displayed. | (1) When LED2 is lit. Check the remote controller wiring for breaking or contact failure. | |
| • ‘PLEASE WAIT is displayed. | (2) When LED2 is blinking. Check short circuit of remote controller wiring. | |
| (3) When LED2 is not lit. Failure of remote controller if "PLEASE WAIT is not displayed | ||
| 2. "PLEASE WAIT display is remained on the remote controller. | At longest 2 minutes after the power supply ‘PLEASE WAIT is displayed to start up. | Normal operation (D Self-diagnosis of remote controller CD'"PLEASE WAIT is displayed for 6 minutes at most in case of indoor/outdoor unit communication error. Check LED3 on indoor controller board. |
| Communication error between the remote controller and indoor unit | (1) When LED3 is not blinking. Check indoor/outdoor connecting wire for Miswiring. | |
| Outdoor unit protection device connector is open. | (2) When LED3 is blinking. Indoor/outdoor connecting wire is normal. | |
| 3. When pressing the remote controller operation switch, the OPERATION display is appeared but it will be turned off soon. | After cancelling to select function from the remote controller, the remote controller operation switch will be not accepted for approx. 30 seconds. | (Normal operation |
| 4. Even controlling by the wireless remote controller, no beep is heard and the unit does not start operating. Operation display is indicated on wireless remote controller. | The pair number settings of the wireless remote controller and indoor controller board are mismatched. | Check the pair number settings. |
| 5. When operating by the wireless remote controller, beep sound is heard, however, unit does not start operating. | No operation for 2 minutes at most after the power supply ON. | Normal operation |
| Local remote controller operation is prohibited. | Check the phenomena No.2. | |
| • Remote controlling adaptor is connected to CN32 on the indoor controller board. | ||
| • Local remote controller operation is prohibited by centralized controller etc. since it is connected to MELANS. | ||
| 6. Remote controller display works normally and the unit performs cooling operation, however, the capacity cannot be fully obtained. (The air does not cool well.) | Refrigerant shortage | • If refrigerant leaks, discharging temperature rises and LEV opening increases. Inspect leakage by checking the temperature and opening. |
| Filter clogging | • Check pipe connections for gas leakage. | |
| Heat exchanger clogging | Open intake grille and check the filter. | |
| Air duct short cycle | Clean the filter by removing dirt or dust on | |
| • If the filter is clogged, indoor pipe temperature rises and discharging pressure increases. Check if heat exchanger is clogged by inspecting discharging pressure. | ||
| • Clean the heat exchanger. | ||
| Remove the blockage. | ||
| 7. Remote controller display works normally and the unit performs heating operation, however, the capacity cannot be fully obtained. | Linear expansion valve fault Opening cannot be adjusted well due to linear expansion valve fault. | Discharging temperature and indoor heat exchanger temperature does not rise. Inspect the failure by checking discharging pressure. • Replace linear expansion valve. |
| Refrigerant shortage | If refrigerant leaks, discharging temperature rises and LEV opening increases. Inspect leakage by checking the temperature and opening. • Check pipe connections for gas leakage. | |
| Lack of insulation for refrigerant piping | Check the insulation. | |
| Filter clogging | Open intake grille and check the filter. | |
| Heat exchanger clogging | Clean the filter by removing dirt or dust on it. | |
| Air duct short cycle | If the filter is clogged, indoor pipe temperature rises and discharging pressure increases. Check if heat exchanger is clogged by inspecting discharging pressure. • Clean the heat exchanger. | |
| Bypass circuit of outdoor unit fault | Remove the blockage. | |
| Check refrigerant system during operation. |
Mitsubishi SUZ-KA15NA.TH Heat Pump Troubleshooting
| LCD | Contents of trouble |
|---|---|
| P1 | Abnormality of room temperature thermistor |
| P2 | Abnormality of pipe temperature thermistor/Liquid |
| P4 | Abnormality of drain sensor/ Float switch connector open |
| P6 | Freezing/overheating protection is operating. |
| P8 | Abnormality of pipe temperature |
| P9 | Abnormality of pipe temperature thermistor/Cond./Eva |
| Fb | Abnormality of indoor controller board |
| U1-UP | Malfunction outdoor unit |
| F3-F9 | Malfunction outdoor unit |
| E0-E5 | Remote controller transmitting error |
| E6-EF | Indoor/outdoor, unit, communication error |
| — | No error history |
| FFFF | No applied unit |
| PA | Forced compressor stop(due to water leakage abnormality) |
Mitsubishi PRH-P16MYA Heat Pump Troubleshooting
| Remote Controller Display Symptoms | OUTDOOR BOARD LED Display Symptoms | Cause |
|---|---|---|
| Remote controller displays "PLEASE WAIT", and cannot be operated. | After "startup" is displayed, only queen lights up. | • After power is turned on, "PLEASE WAIT" is displayed for 2 minutes during system startup. (Normal) |
| After power is turned on, "PLEASE WAIT" is displayed for 3 minutes, then error code is displayed. | After "startup" is displayed, green (once) and red (once) blink alternately. | • Incorrect connection of outdoor terminal block |
| After "startup" is displayed, green (once) and red (twice) blink alternately. | • Outdoor unit's protection devise connector is open. | |
| No display appears even when remote controller operation switch is turned on. (Operation lamp does not light up.) | After "startup" is displayed, green (twice) and red (once) blink alternately. | • Incorrect wiring between the indoor and outdoor unit |
| • Remote controller transmission wire short. | ||
| After "startup" is displayed, only green lights up. <00> | • There is no outdoor unit of address 0. (Address is other than 0.) | |
| • Remote controller transmission wire open. | ||
| Display appears but soon disappears even when remote controller is operated. | After "startup" is displayed, only green lights up. <00> | • After canceling function selection, operation is not possible for about 30 seconds. (Normal) |