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 | Severity |
|---|---|---|
| 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 |
| 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 |
| E11 (Ducted and KX systems with multiple indoor units) | The indoor unit addresses have not been set correctly. | Minor fault |
| 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 |
| E14 (Ducted and cassette systems with master and slave wall controllers) | The master and slave wall controllers are not set up correctly. | Minor fault |
| 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 |
| 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 |
| E19 (Ducted and cassette indoor units) | The indoor unit has been left in its installer check mode. | Minor fault |
| 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 |
| E20 (Ducted and cassette indoor units) | The indoor fan motor speed reading is abnormal. | Fault – service needed |
| 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 |
| E28 (Systems with a wired wall controller) | The temperature sensor built into the wall controller is faulty. | Minor fault |
| 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 |
| E31 (KX systems with multiple outdoor units) | Two outdoor units on the same network have been given the same address. | Minor fault |
| 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 |
| E33 (Ducted and packaged systems) | The outdoor unit has measured abnormal electrical current on the inverter power input. | Fault – service needed |
| E34 (Three phase ducted and packaged systems) | The outdoor unit has detected a missing phase in its power supply. | Fault – service needed |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| E49 (Ducted, packaged and KX systems) | Refrigerant pressure has dropped too low, so the system has stopped. | Fault – service needed |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| E59 (Ducted, cassette (PAC) and KX systems) also shown as E59-1, E59-2 |
The compressor failed to start. | Fault – service needed |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| E7 (Ducted, cassette and multi-head indoor units) | The return air temperature sensor is giving a faulty reading. | Fault – service needed |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
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
What does Mitsubishi Heavy Industries fault code E36 mean? (All systems (split, ducted, multi-head and cassette))
The compressor has run too hot, so the system has shut down to protect it.
Likely causes:
- Refrigerant shortage from a leak
- Service valve not fully open
- Faulty discharge pipe sensor
- Restricted airflow
Safe checks before you call:
- Clear leaves, weeds and stored items away from the outdoor unit so air can flow freely around it
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
- If the fault comes back after a restart, stop using the system until it is checked
What does Mitsubishi Heavy Industries fault code E40 mean? (All systems (split, ducted, multi-head and cassette))
Refrigerant pressure has risen too high, or the outdoor unit’s gas service valve is closed, so the system has stopped.
Likely causes:
- Service valve left closed after installation or service
- Blocked airflow through the indoor or outdoor unit
- Dirty return air filters while heating
- Faulty high pressure sensor or switch
- Faulty outdoor circuit board
Safe checks before you call:
- Clean the return air filters if they are dusty
- Clear leaves, weeds and stored items away from the outdoor unit so air can flow freely around it
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
- If the fault comes back after a restart, stop using the system until it is checked
What does Mitsubishi Heavy Industries fault code E63 mean? (KX ducted and multi-head systems with an emergency stop input)
The system has been stopped by an external emergency stop signal.
Likely causes:
- Emergency stop input activated by connected external equipment
- Building safety interlock triggered
- Wiring fault on the external input terminal
Safe checks before you call:
- Check whether another system in the building (such as a fire or safety panel) has triggered the stop, then contact your technician
What does Mitsubishi Heavy Industries fault code E3 mean? (Splits and KX systems)
The indoor unit cannot find the outdoor unit on the signal line.
Likely causes:
- No power reaching the outdoor unit
- Mismatched pairing between indoor and outdoor units
- Missing, broken or loose signal wiring
- Faulty indoor or outdoor circuit board
Safe checks before you call:
- Check the isolator switch next to the outdoor unit is turned on
- Check your switchboard for a tripped circuit breaker and reset it if it is safe to do so
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E5 mean? (All systems (split, ducted, multi-head and cassette))
The indoor and outdoor units have stopped talking to each other.
Likely causes:
- Damaged or loose interconnecting cable between the units
- Power lost to the outdoor unit
- Faulty indoor or outdoor circuit board
- Address setting error on multi-unit systems
- Wall controller wiring fault or unit address error (KX systems, where E5 means communication was lost during operation)
Safe checks before you call:
- Check the isolator switch next to the outdoor unit is turned on
- Check your switchboard for a tripped circuit breaker and reset it if it is safe to do so
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E6 mean? (Ducted, cassette and multi-head indoor units)
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.
Likely causes:
- Broken sensor wire or loose connector
- Faulty sensor element
- Faulty indoor circuit board
- Service valve on the outdoor unit left closed (older multi-head systems)
Safe checks before you call:
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E7 mean? (Ducted, cassette and multi-head indoor units)
The return air temperature sensor is giving a faulty reading.
Likely causes:
- Broken sensor wire or loose connector
- Faulty sensor element
- Faulty indoor circuit board
Safe checks before you call:
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E8 mean? (Ducted and cassette systems)
The indoor coil has become too hot while heating, so the unit has stopped to protect itself.
Likely causes:
- Dirty return air filters restricting airflow
- Closed or blocked supply and return vents
- Faulty indoor coil sensor
- Faulty indoor circuit board
Safe checks before you call:
- Clean the return air filters if they are dusty
- Make sure supply and return air vents are open and not covered by furniture or rugs
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E9 mean? (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.
Likely causes:
- Blocked condensate drain line
- Faulty drain pump or broken drain pump wiring
- Float switch stuck or faulty
- Drain pipe installed at the wrong fall
Safe checks before you call:
- Look at where the drain pipe ends outside and clear any visible dirt, mulch or debris away from the outlet
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E16 mean? (All systems (split, ducted, multi-head and cassette))
The indoor fan motor is not spinning at the speed it should, so the unit has stopped.
Likely causes:
- Faulty indoor fan motor
- Loose or poor motor connector connection
- Something jamming the fan
- Faulty indoor circuit board or blown fuse
Safe checks before you call:
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E20 mean? (Ducted and cassette indoor units)
The indoor fan motor speed reading is abnormal.
Likely causes:
- Faulty indoor fan motor
- Something caught in the fan
- Faulty indoor power circuit board
- Electrical noise or a blown fuse
Safe checks before you call:
- Turn the system off at the isolator or circuit breaker, wait five minutes, then turn it back on and try again
What does Mitsubishi Heavy Industries fault code E32 mean? (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.
Likely causes:
- Tripped breaker or blown fuse on one phase at the switchboard
- Fault in the incoming power supply
- Faulty outdoor circuit board
Safe checks before you call:
- Check your switchboard for a tripped circuit breaker and reset it if it is safe to do so
Fault confirmed? Here is what to do next
A fault code is the starting point, not the fix. Start here:
- Air conditioner repairs – how we diagnose and fix Mitsubishi Heavy Industries faults across Adelaide. Our fault find covers the full diagnosis, and it is on us if you go ahead with the repair.
- Repair or replace calculator – whether fixing your current system is the smarter money.
- Service and maintenance – regular servicing prevents most of the faults on this page.
- Air conditioner fault code lookup – all 15 brands in one place.
- All calculators and tools
Call us on 08 8296 7888 or book online and we will call or text you back ASAP.
Sources for this page
Every Mitsubishi Heavy Industries code above is checked against these Australian documents. Open them yourself to verify anything on this page:
- service support handbook (mhiaa.com.au)
- mitsubishi air conditioning error codes (extrordinair.com.au)
- mitsubishi heavy industries error codes (compareairconditioning.com.au)
Mitsubishi Heavy Industries fault code FAQs
Where do I find the fault code on a Mitsubishi Heavy Industries air conditioner?
Check the remote or wall controller display first. Some models flash the indoor unit’s lamps in a pattern instead; the table above lists documented lamp patterns alongside their codes. If nothing is showing, the code may only appear while the fault is active.
Can I clear a Mitsubishi Heavy Industries fault code myself?
You can reset the system by turning it off at the isolator or breaker for five minutes. If the code stays gone, it was a one-off. If it returns, the fault is real and needs a licensed technician, and repeated resets can cause further damage on compressor or refrigerant faults.
Does a Mitsubishi Heavy Industries fault code mean I need a new air conditioner?
Usually not. Most codes point to repairable faults like sensors, fan motors or drainage. Our fault find gives you an honest verdict either way, and the fee is credited if you repair with us.
Are these Mitsubishi Heavy Industries fault codes correct for Australian models?
Yes. Every code on this page was checked against Australian documentation (mhiaa.com.au, extrordinair.com.au, compareairconditioning.com.au), not overseas lists, because the same code can mean different things in different markets. Meanings still vary between model series, so treat this page as reference and cross-check your unit’s manual.
Written by Oliver Hastings, T&K Airpower. Last updated 01/08/2026. Compiled from Australian sources including mhiaa.com.au, extrordinair.com.au, compareairconditioning.com.au, so you can check every code against the official documentation. Fault code meanings vary between model series and controllers, so treat this page as reference only and never remove panels or work on the refrigeration or electrical parts of the system yourself.
