Mitsubishi Heat Pump Troubleshooting

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 lampAbnormal point (Failure mode)Condition
Not lightedNormal
1-time flash every 0.5-secondRoom temperature thermistorThe room temperature thermistor short or open circuit is detected every 8 seconds during operation.
2-time flash 2.5-second OFFIndoor coil thermistorThe indoor coil thermistor short or open circuit is detected every 8 seconds during operation.
3-time flash 2.5-second OFFSerial signalThe serial signal from outdoor unit is not received for a maximum of 6 minutes.
11-time flash 2.5-second OFFIndoor fan motorThe rotational frequency feedback signal is not emitted for 12 seconds after the indoor fan motor is operated.
12-time flash 2.5-second OFFIndoor control systemIt cannot properly read data in the nonvolatile memory of the indoor electronic control RC board.

Mitsubishi EHSC Series Heat Pump Troubleshooting

DisplayContents to be inspected (During operation)
U1Abnormal high pressure (63H operated)
U2Abnormal high discharging temperature and shell thermistor, shortage of refrigerant
U3Open/short circuit of discharging thermistor(TH4) and shell thermistor(TH32)
U4Open/short of outdoor unit thermistors(TH3, TH6, TH7 and TH8)
U5Abnormal temperature of heat sink
U6Abnormality of power module
U7Abnormality of superheat due to low discharge temperature
U8Abnormality in outdoor fan motor
UdOverheat protection
UFCompressor overcurrent interruption (When Comp, locked)
UHCurrent sensor error
ULAbnormal low pressure
UPCompressor overcurrent interruption
P1-P8Abnormality of indoor units
A0-A7Communication error of M-NET system

Mitsubishi Mr. Slim Heat Pump Troubleshooting

DisplayContents to be inspected (When power is turned on)
F563H connector(yellow) is open.
E8Indoor/outdoor communication error (Signal receiving error) (Outdoor unit)
E9Indoor/outdoor communication error (Transmitting error) (Outdoor unit)
EAMisfiring of indoor/outdoor unit connecting wire, excessive number of indoor units (4 units or more)
EbMisfiring of indoor/outdoor unit connecting wire(converse wiring or disconnection)
ECStartup time over
E0-E7Communication error except for outdoor unit

Mitsubishi PQRY-P144YSLMU-A Heat Pump Troubleshooting

Beeper sounds/OPERATION INDICATOR lamp flashes (Number of times)Check codeSymptom
1P1Intake sensor error
2P2Pipe (TH2) sensor error
P9Pipe (TH5) sensor error
3E6.E7Indoor/outdoor unit communication error
4P4Drain sensor error/Float switch connector (CN4F) open
5P5Drain pump error
PAForced compressor stop (due to water leakage abnormality)
6P6Freezing/Overheating protection operation
7EECommunication error between indoor and outdoor units
8P8Pipe temperature error
9E4, E5Remote controller signal receiving error
10--
11--
12FbIndoor unit control system error (memory error, etc.)
-EO, E3Remote controller transmission error
-El, E2Remote controller control board error

Mitsubishi PUHZ-HW140VHA2-BS Heat Pump Troubleshooting

Beeper sounds/OPERATION INDICATOR lamp flashes (Number of times)Check codeSymptom
1E9Indoor/outdoor unit communication error (Transmitting error) (Outdoor unit)
2UPCompressor overcurrent interruption
3U3.U4Open/short of outdoor unit thermistors
4UFCompressor overcurrent interruption (When compressor locked)
5U2Abnormal high discharging temperature/insufficient refrigerant
6U1,UdAbnormal high pressure (63H operated)/Overheating protection operation
7U5Abnormal temperature of heatsink
8U8Outdoor unit fan protection stop
9U6Compressor overcurrent interruption/Abnormal of power module
10U7Abnormality of superheat due to low discharge temperature
11U9.UHAbnormality such as overvoltage or voltage shortage and abnormal synchronous signal to main circuit/Current sensor error
12--
13--
14OthersOther errors

Mitsubishi QAHV Heat Pump Troubleshooting

Error codeInspected content
U4Open/short of outdoor unit thermistor (TH3/TH6/TH7/TH8)
E8Indoor/outdoor unit communication error
• Signal receiving error (Outdoor unit)
E9Indoor/outdoor unit communication error
• Transmitting error (Indoor unit)
EO - E7Communication error other than outdoor unit
EdCommunication error between outdoor controller board and M-NET board (Serial communication error)

Mitsubishi SEZ-KD09NA4.TH Heat Pump Troubleshooting

PhenomenaFactorCountermeasure
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 cloggingOpen intake grille and check the filter.
Air duct short cycleClean 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 shortageIf 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 pipingCheck the insulation.
Filter cloggingOpen intake grille and check the filter.
Heat exchanger cloggingClean the filter by removing dirt or dust on it.
Air duct short cycleIf 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 faultRemove the blockage.
Check refrigerant system during operation.

Mitsubishi SUZ-KA15NA.TH Heat Pump Troubleshooting

LCDContents of trouble
P1Abnormality of room temperature thermistor
P2Abnormality of pipe temperature thermistor/Liquid
P4Abnormality of drain sensor/ Float switch connector open
P6Freezing/overheating protection is operating.
P8Abnormality of pipe temperature
P9Abnormality of pipe temperature thermistor/Cond./Eva
FbAbnormality of indoor controller board
U1-UPMalfunction outdoor unit
F3-F9Malfunction outdoor unit
E0-E5Remote controller transmitting error
E6-EFIndoor/outdoor, unit, communication error
No error history
FFFFNo applied unit
PAForced compressor stop(due to water leakage abnormality)

Mitsubishi PRH-P16MYA Heat Pump Troubleshooting

Remote Controller Display SymptomsOUTDOOR BOARD LED Display SymptomsCause
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)