Hitachi Air Conditioner Fault Codes

What does your Hitachi 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 58 Hitachi fault codes for units sold in Australia, compiled from official Australian manufacturer and distributor documentation, the same references our own technicians carry.

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

Every Hitachi 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
01 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 01	The indoor unit’s safety float switch has tripped, usually because condensate water is not draining away properly.	Fault – service needed
02 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 02	The outdoor unit has shut itself down on its high pressure safety cut-out.	Fault – service needed
03 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 03	The indoor and outdoor units have stopped communicating with each other.	Fault – service needed
04 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 04	Communication has failed between the inverter circuit board and the main circuit board inside the outdoor unit.	Fault – service needed
05 (Three phase ducted and VRF systems) also shown as Alarm code 05	The three phase power supply to the unit is abnormal, usually because the phases are connected in the wrong order.	Fault – service needed
06 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 06	The inverter has detected abnormal voltage in its power circuit.	Fault – service needed
07 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 07	The refrigerant leaving the compressor is not as hot as it should be, which can mean liquid refrigerant is flooding back to the compressor.	Fault – service needed
08 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 08	The temperature at the top of the compressor is too high.	Fault – service needed
0A (VRF systems with more than one outdoor unit) also shown as Alarm code 0A	The outdoor units on the system are not communicating with each other.	Fault – service needed
0C (VRF systems with more than one outdoor unit; usually seen at installation) also shown as Alarm code 0C	The main outdoor unit setting is wrong, such as two outdoor units both set as the main unit.	Fault – service needed
0b (VRF systems with more than one outdoor unit; usually seen at installation) also shown as Alarm code 0b	The address settings for the outdoor units are incorrect.	Fault – service needed
1 blink (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); the fault shows as counted flashes of the timer lamp) also shown as Timer lamp flashes once, pauses, then repeats	There is a problem in the refrigerant cycle, commonly low refrigerant from a leak.	Fault – service needed
1 blink (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes once, pauses, then repeats when checking a fault	The outdoor unit is waiting to start or has stopped normally, such as after fan only mode; this is normal operation rather than a fault.	Normal operation
10 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 10 times, pauses, then repeats	The indoor fan motor is drawing too much current, often because the fan is jammed or the motor is failing.	Fault – service needed
10 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 10 times, pauses, then repeats when checking a fault	The power supply reaching the outdoor unit is outside the normal range, or an internal power component is disconnected.	Fault – service needed
11 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 11	The sensor that measures the air entering the indoor unit is faulty.	Minor fault
11 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 11 times, pauses, then repeats when checking a fault	Strong wind is blowing backwards through the outdoor unit and has stopped the fan; the unit restarts itself once the wind eases.	Normal operation
12 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 12 times, pauses, then repeats	The signal from the outdoor unit is being interrupted, pointing to an outdoor interface fault or a wiring problem.	Fault – service needed
12 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 12 times, pauses, then repeats when checking a fault	The outdoor fan has stopped or jammed, sometimes just from strong wind blowing back through the unit.	Fault – service needed
13 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 13	The temperature sensor on the indoor unit’s pipework is faulty.	Minor fault
13 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 13 times, pauses, then repeats	The indoor unit cannot read its memory chip correctly.	Fault – service needed
14 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 14 times, pauses, then repeats when checking a fault	The outdoor unit’s power correction circuit has detected abnormal voltage.	Fault – service needed
15 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 15 times, pauses, then repeats when checking a fault	The outdoor unit’s electronic circuit has an internal fault.	Fault – service needed
16 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 16 times, pauses, then repeats when checking a fault	The system has shut down because it is working too hard, commonly from blocked airflow or a valve left closed after installation.	Fault – service needed
18 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 18	The protection device for the indoor fan motor’s inverter circuit board has tripped.	Fault – service needed
19 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 19	The indoor fan motor’s protection has tripped, usually because the motor overheated or jammed.	Fault – service needed
2 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes twice, pauses, then repeats	The outdoor unit is running a forced or balancing operation, which is a service mode rather than a breakdown.	Normal operation
2 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes twice, pauses, then repeats when checking a fault	The outdoor unit has cut power to the compressor because it was drawing too much current.	Fault – service needed
20 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 20	The temperature sensor on the compressor is faulty.	Minor fault
21 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 21	The high pressure sensor on the outdoor unit is faulty.	Minor fault
21 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 21 times, pauses, then repeats	Communication between the units is being disrupted by another appliance or an external interference source.	Minor fault
22 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 22	The outdoor air temperature sensor is faulty.	Minor fault
23 (VRF and larger inverter systems) also shown as Alarm code 23	The sensor that measures the temperature of gas leaving the compressor is faulty.	Minor fault
24 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes)) also shown as Alarm code 24	The temperature sensor on the liquid side of the outdoor coil is faulty.	Minor fault
25 (VRF and larger inverter systems) also shown as Alarm code 25	A temperature sensor on the gas side of the outdoor unit’s heat exchanger is faulty.	Minor fault
25 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 25 times, pauses, then repeats	Two network or Wi-Fi adapters are plugged in at once, or an adapter is connected incorrectly.	Minor fault
3 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 3 times, pauses, then repeats	The indoor unit’s interface circuit board has a fault.	Fault – service needed
3 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 3 times, pauses, then repeats when checking a fault	The compressor is not spinning properly at low speed, which points to a compressor or outdoor circuit board problem.	Fault – service needed
31 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes); usually seen at installation or after board replacement) also shown as Alarm code 31	The outdoor unit and indoor units are set to an incompatible capacity combination.	Fault – service needed
31 (VRF systems with more than one outdoor unit) also shown as Alarm code 31	The main outdoor unit has lost communication with all of its secondary outdoor units.	Fault – service needed
35 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems; usually seen at installation) also shown as Alarm code 35	The indoor unit numbering is set incorrectly, such as two indoor units sharing the same number on one system.	Fault – service needed
36 (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems; usually seen at installation) also shown as Alarm code 36	An indoor unit connected to the system is not a compatible model for the outdoor unit.	Fault – service needed
3d (VRF systems with more than one outdoor unit) also shown as Alarm code 3d	The main outdoor unit has lost communication with one of its secondary outdoor units.	Fault – service needed
4 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 4 times, pauses, then repeats	The outdoor unit’s electrical assembly has a fault.	Fault – service needed
4 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 4 times, pauses, then repeats when checking a fault	The outdoor unit cannot switch the compressor windings correctly, usually because a compressor connector is loose or the outdoor board is failing.	Fault – service needed
48 (VRF and larger inverter systems) also shown as Alarm code 48	The compressor’s overcurrent protection device has tripped.	Fault – service needed
5 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 5 times, pauses, then repeats when checking a fault	The outdoor unit keeps hitting its overload protection, often because its airflow is blocked.	Fault – service needed
51 (VRF and larger inverter systems) also shown as Alarm code 51	The current sensor for the inverter is faulty.	Fault – service needed
53 (VRF and larger inverter systems) also shown as Alarm code 53	The inverter has detected an internal error signal and shut down to protect the compressor.	Fault – service needed
54 (VRF and larger inverter systems) also shown as Alarm code 54	The inverter’s heat sink is running too hot.	Fault – service needed
6 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 6 times, pauses, then repeats when checking a fault	The compressor’s overheat sensor is reading too hot, which commonly points to low refrigerant from a leak.	Fault – service needed
7 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 7 times, pauses, then repeats when checking a fault	A temperature sensor in the outdoor unit is faulty or unplugged.	Minor fault
9 blinks (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series)) also shown as Timer lamp flashes 9 times, pauses, then repeats	A temperature or humidity sensor in the indoor unit is faulty.	Minor fault
9 blinks (operation lamp) (Wall mounted splits and multi-head indoor units without a code display (airHome 400, 500, 600 and P series); shown on the OPERATION lamp when the fault sits in the outdoor unit) also shown as Operation lamp flashes 9 times, pauses, then repeats when checking a fault	The outdoor unit has lost communication with the indoor unit, usually a connecting cable problem.	Fault – service needed
C1 (Heat recovery VRF systems with a CH box; usually seen at installation) also shown as Alarm code C1	An indoor unit is connected to the wrong port on the system’s CH box.	Fault – service needed
C2 (Heat recovery VRF systems with a CH box; usually seen at installation) also shown as Alarm code C2	Too many indoor units are connected to one CH box on the system.	Fault – service needed
C3 (Heat recovery VRF systems with a CH box; usually seen at installation) also shown as Alarm code C3	An indoor unit connected through the system’s CH box has the wrong refrigerant cycle number set.	Fault – service needed
C5 (Heat recovery VRF systems with a CH box; usually seen at installation) also shown as Alarm code C5	The port settings on the system’s CH box do not match how the indoor units are actually connected.	Fault – service needed

The most serious Hitachi fault codes explained

What does Hitachi fault code 01 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The indoor unit’s safety float switch has tripped, usually because condensate water is not draining away properly.

Likely causes:

• Blocked or kinked condensate drain pipe
• High water level in the drain pan
• Failed condensate drain pump
• Faulty float switch

Safe checks before you call:

• If you can see the end of the drain pipe outside, check it is not blocked by dirt or garden debris
• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, stop and book a service

What does Hitachi fault code 02 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The outdoor unit has shut itself down on its high pressure safety cut-out.

Likely causes:

• Blocked or dirty outdoor coil, or airflow around the outdoor unit restricted
• Refrigerant pipe blockage
• Too much refrigerant in the system
• Outdoor fan motor not running during cooling

Safe checks before you call:

• Check the outdoor unit is not covered or crowded by plants, leaves, bins or stored items and has clear airflow
• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, stop and book a service

What does Hitachi fault code 03 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The indoor and outdoor units have stopped communicating with each other.

Likely causes:

• Loose terminals or a disconnected interconnecting wire
• Incorrect wiring between indoor and outdoor units
• Blown fuse on a circuit board
• Power to the outdoor unit switched off

Safe checks before you call:

• Check the outdoor unit isolator switch (next to the outdoor unit) is turned on
• Check the air conditioner breaker in your switchboard has not tripped
• Turn the system off at the isolator or breaker for 5 minutes, then restart

What does Hitachi fault code 04 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

Communication has failed between the inverter circuit board and the main circuit board inside the outdoor unit.

Likely causes:

• Loose connector inside the outdoor unit
• Broken wire between the two boards
• Blown fuse
• Failing inverter or outdoor circuit board

Safe checks before you call:

• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, book a service

What does Hitachi fault code 05 mean? (Three phase ducted and VRF systems)

The three phase power supply to the unit is abnormal, usually because the phases are connected in the wrong order.

Likely causes:

• Reverse phase due to incorrect wiring at installation
• A lost or dropped supply phase

Safe checks before you call:

• Check whether other three phase equipment in the property has also stopped, which can point to a supply problem
• Turn the system off at the breaker for 5 minutes, then restart; if the code returns, book a service

What does Hitachi fault code 06 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The inverter has detected abnormal voltage in its power circuit.

Likely causes:

• Problem with the incoming power supply voltage
• Failing inverter board
• Failing fan controller or related electronics

Safe checks before you call:

• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, book a service

What does Hitachi fault code 07 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The refrigerant leaving the compressor is not as hot as it should be, which can mean liquid refrigerant is flooding back to the compressor.

Likely causes:

• Too much refrigerant in the system
• Expansion valve stuck open or its connector disconnected
• Faulty temperature sensor
• Incorrect wiring or piping connection

Safe checks before you call:

• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, book a service

What does Hitachi fault code 08 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The temperature at the top of the compressor is too high.

Likely causes:

• Refrigerant shortage from a leak
• Refrigerant pipe blockage
• Expansion valve problem

Safe checks before you call:

• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, stop using the system and book a service

What does Hitachi fault code 18 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The protection device for the indoor fan motor’s inverter circuit board has tripped.

Likely causes:

• Indoor fan motor circuit board fault
• Fan motor overload

Safe checks before you call:

• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, book a service

What does Hitachi fault code 19 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes))

The indoor fan motor’s protection has tripped, usually because the motor overheated or jammed.

Likely causes:

• Fan motor overheating
• Fan jammed or locked up
• Failing fan motor

Safe checks before you call:

• Clean or check the return air filters if they are the easy access slide out type, as heavily blocked filters make the fan work harder
• Turn the system off at the isolator or breaker for 5 minutes, then restart; if the code returns, book a service

What does Hitachi fault code 31 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems (multi-head RAM systems show timer lamp flashes instead of two digit codes); usually seen at installation or after board replacement)

The outdoor unit and indoor units are set to an incompatible capacity combination.

Likely causes:

• Incorrect capacity code setting after a circuit board change
• Total indoor unit capacity too high or too low for the outdoor unit

Safe checks before you call:

• Turn the system off at the isolator or breaker for 5 minutes, then restart; this code is a setup issue that your installer or service company needs to correct

What does Hitachi fault code 35 mean? (Ducted, cassette and single split systems with a Hitachi wall controller, and VRF systems; usually seen at installation)

The indoor unit numbering is set incorrectly, such as two indoor units sharing the same number on one system.

Likely causes:

• Duplicate indoor unit number in the same refrigerant group
• Indoor unit number set outside the allowed range

Safe checks before you call:

• This is a setup issue rather than a breakdown; your installer or service company needs to correct the unit addressing

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 Hitachi 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 Hitachi code above is checked against these Australian documents. Open them yourself to verify anything on this page:

• HIT0924 Hitachi Service Training Manual 2024 (PDF) (temperzone.com)
• alarm code troubleshooting 1 (hitachiaircon.com/au)
• hitachi air conditioner error codes video tutorials for professionals (hitachiaircon.com/au)

Hitachi fault code FAQs

Written by Oliver Hastings, T&K Airpower. Last updated 01/08/2026. Compiled from Australian sources including temperzone.com, hitachiaircon.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.