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Mitsubishi Heavy Industries Air Conditioner Fault Codes

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What does your Mitsubishi Heavy Industries fault code mean?

Pick the code showing on your remote, wall controller or indoor unit and see what it means, what commonly causes it, and what is safe to check yourself. This page covers 54 Mitsubishi Heavy Industries fault codes for units sold in Australia, compiled from official Australian manufacturer and distributor documentation, the same references our own technicians carry.

Heads up: Mitsubishi Heavy Industries uses the same code with different meanings on different product ranges, so check the model range shown next to the code.

Every Mitsubishi Heavy Industries fault code at a glance

Some models show faults as a flashing-light pattern instead of a code; documented lamp patterns are listed alongside their codes.

Code	What it means	How serious	Most likely cause	What you can check yourself
E1 (Systems with a wired wall controller (ducted, cassette, multi-head and splits with an optional wired remote))	The wired wall controller has lost communication with the indoor unit.	Minor fault	Broken or incorrectly connected controller wiring	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E10 (Ducted and KX systems with multiple indoor units on one controller)	Too many indoor units are wired to one wall controller (more than 16).	Minor fault	Too many indoor units connected to the one controller	Nothing safe to check yourself. Book a technician.
E11 (Ducted and KX systems with multiple indoor units)	The indoor unit addresses have not been set correctly.	Minor fault	Address setting mistake during installation or service	Nothing safe to check yourself. Book a technician.
E12 (KX ducted and multi-head systems)	Indoor unit addresses were set using a mix of automatic and manual methods, which the system does not allow.	Minor fault	Address setting mistake during installation	Nothing safe to check yourself. Book a technician.
E14 (Ducted and cassette systems with master and slave wall controllers)	The master and slave wall controllers are not set up correctly.	Minor fault	No controller assigned as the master	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E16 (All systems (split, ducted, multi-head and cassette))also shown as Run light flashes 6 times, Timer light on (hi-wall splits)*	The indoor fan motor is not spinning at the speed it should, so the unit has stopped.	Fault – service needed	Faulty indoor fan motor	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E18 (KX ducted and multi-head systems with master and slave indoor units)	The master and slave indoor unit addresses are not set correctly.	Minor fault	Address setting error on the master indoor unit	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E19 (Ducted and cassette indoor units)	The indoor unit has been left in its installer check mode.	Minor fault	Service switch left in the check position after installation or maintenance	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E2 (KX ducted and multi-head systems with several indoor units on one network)	The system has found two indoor units set to the same address, so it cannot tell them apart.	Minor fault	Address setting mistake during installation	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E20 (Ducted and cassette indoor units)	The indoor fan motor speed reading is abnormal.	Fault – service needed	Faulty indoor fan motor	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E21 (Cassette systems (FDT series) with the panel switch, and splits with an air inlet panel)	The unit thinks its air inlet panel or filter panel is open or not seated properly.	Minor fault	Return air grille or filter panel not clicked fully shut after filter cleaning	If you have recently cleaned the filters, check the return air grille or panel is latched fully shut
E28 (Systems with a wired wall controller)	The temperature sensor built into the wall controller is faulty.	Minor fault	Broken sensor wire inside the controller	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E3 (Splits and KX systems)also shown as Run light on, Timer light flashes 6 times (hi-wall splits, shared with E5)*	The indoor unit cannot find the outdoor unit on the signal line.	Fault – service needed	No power reaching the outdoor unit	Check the isolator switch next to the outdoor unit is turned on
E31 (KX systems with multiple outdoor units)	Two outdoor units on the same network have been given the same address.	Minor fault	Address setting mistake on the outdoor units	Nothing safe to check yourself. Book a technician.
E32 (KX systems (including ducted and cassette indoor units connected to a KX outdoor unit))	One phase of the three phase power supply is missing, or the phases are connected in the wrong order.	Fault – service needed	Tripped breaker or blown fuse on one phase at the switchboard	Check your switchboard for a tripped circuit breaker and reset it if it is safe to do so
E33 (Ducted and packaged systems)	The outdoor unit has measured abnormal electrical current on the inverter power input.	Fault – service needed	Power supply problem	Check your switchboard for a tripped circuit breaker and reset it if it is safe to do so
E34 (Three phase ducted and packaged systems)	The outdoor unit has detected a missing phase in its power supply.	Fault – service needed	Tripped breaker or blown fuse on one phase at the switchboard	Check your switchboard for a tripped circuit breaker and reset it if it is safe to do so
*E35 (All systems (split, ducted, multi-head and cassette))also shown as Run light on, Timer light keeps flashing (hi-wall splits)*	The outdoor coil has become too hot while cooling, so the system has stopped to protect itself.	Fault – service needed	Blocked or dirty outdoor coil, or hot air trapped around the outdoor unit	Clear leaves, weeds and stored items away from the outdoor unit so air can flow freely around it
*E36 (All systems (split, ducted, multi-head and cassette))also shown as E36-1, E36-2, Run light on, Timer light flashes 5 times (hi-wall splits)*	The compressor has run too hot, so the system has shut down to protect it.	Urgent – turn it off	Refrigerant shortage from a leak	Clear leaves, weeds and stored items away from the outdoor unit so air can flow freely around it
E36-3 (KX6 ducted and multi-head systems)	Liquid refrigerant is flooding back to the compressor instead of gas, so the system has stopped to protect it.	Fault – service needed	Refrigerant overcharge	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E37 (All systems (split, ducted, multi-head and cassette))also shown as E37-1, E37-2, E37-3, E37-4, E37-5, E37-6, Run light keeps flashing, Timer light flashes 2 times (hi-wall splits)*	An outdoor coil temperature sensor is giving a faulty reading (on KX systems, E37-5 and E37-6 are the sub cooling coil sensors).	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E38 (All systems (split, ducted, multi-head and cassette))also shown as Run light keeps flashing, Timer light flashes 1 time (hi-wall splits)*	The outdoor air temperature sensor is giving a faulty reading.	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E39 (All systems (split, ducted, multi-head and cassette))also shown as E39-1, E39-2, Run light keeps flashing, Timer light flashes 4 times (hi-wall splits)*	The compressor discharge pipe temperature sensor is giving a faulty reading.	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E40 (All systems (split, ducted, multi-head and cassette))also shown as Run light flashes 7 times, Timer light flashes 1 time (hi-wall splits)*	Refrigerant pressure has risen too high, or the outdoor unit’s gas service valve is closed, so the system has stopped.	Urgent – turn it off	Service valve left closed after installation or service	Clean the return air filters if they are dusty
E41 (Multi-head, ducted, cassette (PAC) and KX systems)also shown as E41-1, E41-2, Run light on, Timer light flashes 4 times (older multi-head heads), Run light keeps flashing, Timer light flashes 6 times (older multi-head heads)	The outdoor unit’s inverter power transistor has overheated or failed, or its temperature sensor is faulty.	Fault – service needed	Restricted airflow over the outdoor unit’s electronics	Clear leaves, weeds and stored items away from the outdoor unit so air can flow freely around it
*E42 (All systems (split, ducted, multi-head and cassette))also shown as E42-1, E42-2, Run light on, Timer light flashes 1 time (hi-wall splits)*	The compressor drew too much electrical current and was shut down (current cut).	Fault – service needed	Compressor locked or seized	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E43 (KX ducted and multi-head systems)also shown as E43-1, E43-2*	More indoor units, or more total indoor capacity, are connected than the outdoor unit supports.	Minor fault	Address setting mistake on indoor or outdoor units	Nothing safe to check yourself. Book a technician.
*E44 (Ducted, packaged and KX systems)also shown as E44-1, E44-2*	Liquid refrigerant is flooding back to the compressor instead of gas.	Fault – service needed	Refrigerant overcharge	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E45 (Multi-head, ducted and cassette (PAC) outdoor units and KX systems)also shown as E45-1, E45-2*	The inverter board and the main control board in the outdoor unit have stopped talking to each other.	Fault – service needed	Loose or broken wiring between the outdoor boards	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E46 (KX ducted and multi-head systems)	Indoor unit addresses on the same network were set with a mix of automatic and manual methods.	Minor fault	Address setting mistake during installation	Nothing safe to check yourself. Book a technician.
*E47 (Splits, multi-head, ducted and packaged systems)also shown as Run light flashes 5 times, Timer light on (hi-wall splits)*	The outdoor unit’s active filter has detected abnormal power supply voltage.	Fault – service needed	Wrong voltage connected to the power supply	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E48 (All systems (split, ducted, multi-head and cassette))also shown as E48-1, E48-2, Run light on, Timer light flashes 7 times (hi-wall splits)*	The outdoor fan motor is not spinning properly, so the unit has stopped.	Fault – service needed	Faulty outdoor fan motor	Look through the outdoor unit grille and check nothing like a stick or vine is visibly jamming the fan. Do not put anything through the grille
E49 (Ducted, packaged and KX systems)	Refrigerant pressure has dropped too low, so the system has stopped.	Fault – service needed	Refrigerant shortage from a leak	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E5 (All systems (split, ducted, multi-head and cassette))also shown as Run light on, Timer light flashes 6 times (hi-wall splits)*	The indoor and outdoor units have stopped talking to each other.	Fault – service needed	Damaged or loose interconnecting cable between the units	Check the isolator switch next to the outdoor unit is turned on
*E51 (All systems (split, ducted, multi-head and cassette))also shown as E51-1, E51-2, Run light on, Timer light flashes 4 times (hi-wall splits)*	The inverter power transistor in the outdoor unit has failed or overheated.	Fault – service needed	Faulty power transistor	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E53 (Multi-head, ducted, packaged and KX systems)also shown as E53-1, E53-2*	The compressor suction pipe temperature sensor is giving a faulty reading.	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E54 (Ducted, packaged, multi-head and KX systems)also shown as E54-1, E54-2*	A refrigerant pressure sensor (high or low pressure) is giving a faulty reading.	Fault – service needed	Faulty pressure sensor	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E55 (Ducted, packaged and KX systems)also shown as E55-1, E55-2*	The compressor under dome temperature sensor is giving a faulty reading.	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E56 (KX ducted and multi-head systems)also shown as E56-1, E56-2*	The power transistor temperature sensor is giving a faulty reading.	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E57 (All systems (split, ducted, multi-head and cassette))also shown as Run light flashes 7 times, Timer light on (hi-wall splits)*	The system has detected it is short of refrigerant, or a service valve is closed.	Fault – service needed	Refrigerant leak	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E58 (All systems (split, ducted, multi-head and cassette))also shown as E58-1, E58-2, Run light on, Timer light flashes 3 times (hi-wall splits)*	The compressor cannot keep up with the speed asked of it, so it has been slowed or stopped to protect itself.	Fault – service needed	System working overloaded in very hot conditions or with blocked coils	Clean the return air filters if they are dusty
*E59 (Ducted, cassette (PAC) and KX systems)also shown as E59-1, E59-2*	The compressor failed to start.	Fault – service needed	Faulty compressor motor or bearing	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E59 (Hi-wall splits and SCM multi-head systems)also shown as Run light on, Timer light flashes 2 times (hi-wall splits and multi-head heads)*	The outdoor unit has shut itself down because of an internal fault, or because it is drawing less power than it should.	Fault – service needed	Broken or disconnected compressor wiring	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E6 (Ducted, cassette and multi-head indoor units)also shown as Run light flashes 7 times, Timer light on (older multi-head heads, closed service valve)*	The indoor coil temperature sensor is giving a faulty reading. On older multi-head systems E6 can also mean the unit detected no cooling at the indoor coil, usually because a service valve was left closed.	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E60 (All systems (split, ducted, multi-head and cassette))also shown as E60-1, E60-2, Run light flashes 2 times, Timer light flashes 2 times (hi-wall splits)*	The outdoor unit cannot detect the position of the compressor motor, so the compressor will not run (rotor lock).	Fault – service needed	Faulty compressor	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*E61 (KX systems with multiple outdoor units working together)also shown as E61-1, E61-2*	The master outdoor unit has lost communication with a slave outdoor unit.	Fault – service needed	Signal wiring fault between the outdoor units	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E63 (KX ducted and multi-head systems with an emergency stop input)	The system has been stopped by an external emergency stop signal.	Urgent – turn it off	Emergency stop input activated by connected external equipment	Check whether another system in the building (such as a fire or safety panel) has triggered the stop, then contact your technician
E7 (Ducted, cassette and multi-head indoor units)	The return air temperature sensor is giving a faulty reading.	Fault – service needed	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
E8 (Ducted and cassette systems)	The indoor coil has become too hot while heating, so the unit has stopped to protect itself.	Fault – service needed	Dirty return air filters restricting airflow	Clean the return air filters if they are dusty
E9 (Ducted, cassette and multi-head indoor units fitted with a drain pump)	The drain safety switch has detected condensate water that is not draining away properly.	Fault – service needed	Blocked condensate drain line	Look at where the drain pipe ends outside and clear any visible dirt, mulch or debris away from the outlet
*Run 1 flash + Timer on (Hi-wall splits and multi-head wall-mounted heads)also shown as Run light flashes 1 time, Timer light on (no code on display)*	The indoor coil temperature sensor is giving a faulty reading.	Minor fault	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*Run 2 flashes + Timer on (Hi-wall splits and multi-head wall-mounted heads)also shown as Run light flashes 2 times, Timer light on (no code on display)*	The room temperature sensor is giving a faulty reading.	Minor fault	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*Run 3 flashes + Timer on (Hi-wall splits and multi-head wall-mounted heads)also shown as Run light flashes 3 times, Timer light on (no code on display)*	The second indoor coil temperature sensor is giving a faulty reading.	Minor fault	Broken sensor wire or loose connector	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
*Run 4 flashes + Timer on (Hi-wall splits with the wifi (wireless LAN) module)also shown as Run light flashes 4 times, Timer light on (no code on display)*	The unit has lost contact with its wifi module, so app control may not work; heating and cooling can usually continue.	Minor fault	Faulty wifi interface board	Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again

Codes that mean switch the system off

If your Mitsubishi Heavy Industries unit shows E36, E40, E63, turn the system off at the isolator and leave it off. These faults involve the compressor, refrigerant or electrical protection, and running the unit can cause further damage.

The most serious Mitsubishi Heavy Industries fault codes explained