Hitachi Aircon Fault Codes Singapore (Complete Guide 2026)

Your Hitachi aircon is showing a fault code or you can tell something’s wrong but don’t know how to read what the unit is telling you. You need to know three things: how to display the fault code on your Hitachi unit, what the code means, and whether you can fix it yourself or need to call a technician.

This guide answers all three. At Lion City Aircon, we’ve serviced over 22,000 aircon units across Singapore since 2016, including thousands of Hitachi inverter splits. This page is based on Hitachi’s official inverter fault code documentation cross-checked against what we actually see in real Singapore homes.

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How to Display Your Hitachi Fault Code
Quick Reference Table
Detailed Fault Code Sections
Repair Cost in Singapore
Frequently Asked Questions

How to Display Your Hitachi Fault Code

Hitachi inverter aircons store fault codes in their control board memory. When the unit detects an abnormality, the operation LED or timer LED on the indoor unit usually flashes in a specific pattern, and the wired remote (if you have one) displays the numeric code.

Wired Remote Controller

For Hitachi wired remote controllers (common on cassette, ducted, and commercial units):

When a fault is active, the fault code appears on the remote’s display screen along with the indoor unit number.
If the code has cleared but you want to recall the most recent fault, look for the “Check” or “Fault history” function in the remote’s menu.
The remote shows numeric fault codes (1, 2, 3, etc.) matching the table below.
On some models, the fault code displays alongside a sub-code that identifies the specific component within a fault category.

Wireless Remote (Residential Split Models)

For Hitachi residential split aircons with wireless remotes:

When the indoor unit detects a fault, the operation LED, timer LED, or filter LED flashes in a specific pattern.
Count the number of flashes between pauses. Each flash sequence corresponds to a fault code number.
Some Hitachi models have a Check button on the remote. Press it to display the current fault code on the temperature display.

Indoor Unit LED Patterns

Even without a remote display, the indoor unit’s LED pattern gives you a category:

Slow blinking (1 second on, 1 second off): Usually a communication or sensor issue.
Rapid blinking (4-5 times per second): Usually a compressor or refrigerant cycle issue.
Two LEDs blinking together: Drive board or inverter fault.

If you can’t get a clear code displayed, send us a video of the LED pattern via WhatsApp. We can often identify the fault category from the pattern alone.

How to Read a Hitachi Fault Code

Unlike many other brands, Hitachi uses numeric fault codes rather than letter-prefixed codes. The codes are organised into categories based on which part of the system is affected:

Codes 1-22: Outdoor unit sensors, protection devices, and communication
Codes 45-49: IPM (inverter power module) and outdoor fan motor faults
Codes 91-97: System protection and refrigerant cycle issues
Codes 51-83: Indoor unit faults (sensors, fan motor, drainage)
FE and ER: Display board and remote controller communication errors

Some Hitachi units also display driver board sub-codes (1-30+) when the main code is 45 (IPM fault). These give finer detail about the specific drive circuit issue. We cover the main drive codes below as well.

Quick Reference Table: Hitachi Fault Codes

Code	What it Means	Severity
1	Outdoor ambient temperature sensor fault	Medium
2	Outdoor coil temperature sensor fault	Medium
3	Unit over-current turn off	High
4	EEPROM data error	High
5	Cooling freezing protection or heating overload	Medium
7	Indoor-outdoor communication fault	High
12	Voltage absent phase (3-phase models)	High
13	Compressor overheat protector activated	High
14	High pressure switch / high pressure protection	High
15	Low pressure switch / low pressure protection	High
16	Overload protection in cooling mode	High
17	Discharge temperature sensor fault	Medium
18	AC voltage abnormal (over 275V or under 160V)	High
19	Suction temperature sensor fault	Medium
22	Defrosting sensor fault	Medium
45	IPM (Intelligent Power Module) fault	High
46	IPM and control board communication fault	High
47	Discharge temperature too high	High
48	Outdoor upper DC fan motor fault	High
49	Outdoor lower DC fan motor fault	High
51	Drainage protection (water level too high)	Medium
64	Indoor-outdoor communication fault (alternate)	High
72	Indoor fan motor fault	High
73	Indoor EEPROM Data 1 fault	High
74	Indoor EEPROM Data 2 fault	Medium
81	Indoor ambient temperature sensor fault	Medium
83	Evaporator middle temperature sensor fault	Medium
91	IPM board overheating	High
96	Refrigerant shortage	High
97	4-way valve commutation failure	High
FE	Communication fault between control board and wired remote	Medium
ER	Communication fault between control board and display board	Medium

Outdoor Unit Sensor and Protection Faults (Codes 1-22)

Code 1: Outdoor Ambient Temperature Sensor Fault

The thermistor reading outdoor air temperature has failed. Common causes: loose sensor connector, defective sensor, or sampling circuit on the outdoor PCB has failed. The unit may still run but will operate inefficiently because it can’t read outdoor conditions. Cheap fix (parts under $80, full repair from $130).

Code 2: Outdoor Coil Temperature Sensor Fault

Same as Code 1 but for the thermistor on the outdoor coil. Same fix pattern. Important sensor because it’s used for defrost timing and protection logic.

Code 3: Unit Over-Current Turn Off

The unit detected excessive current draw and shut down to protect itself. Common causes we see in Singapore: low supply voltage forcing the compressor to draw more current to maintain output, mechanical compressor lock, or cooling/heating overload from a dirty unit or restricted airflow. Diagnosis required to identify the specific cause.

Code 4: EEPROM Data Error

The EEPROM chip storing the unit’s configuration has data corruption. Causes: failed EEPROM, control circuit fault, or the chip was inserted in the wrong direction during a previous service. The unit can’t operate normally until the EEPROM is reset or replaced.

Code 5: Cooling Freezing Protection or Heating Overload

The indoor coil temperature is too low (during cooling) or too high (during heating). Most common cause we see: dirty air filter restricting airflow across the coil. Other causes: room temperature extremely low/high, restricted duct length, fan speed set too low, or poor installation with air outlet too close to air inlet. Clean filters first. If Code 5 returns, the coil needs proper cleaning or there’s a refrigerant issue.

Code 7: Indoor and Outdoor Communication Fault

One of the most common Hitachi codes we attend. Communication between indoor and outdoor units has failed. Causes: wrong cable connection, loose communication cable, damaged cable, failed indoor or outdoor PCB, blown communication circuit fuse, or wrong cable specification. First check: is the outdoor unit isolator switch on? Trip switches at the DB box and check the outdoor power supply.

Code 12: Voltage Absent Phase (3-Phase Models)

For 3-phase Hitachi units (mostly commercial). One of the three phases isn’t reaching the outdoor unit. Causes: power supply phase loss, incorrect wiring, or PCB fault. Needs electrician verification.

Code 13: Compressor Overheat Protector Device

The compressor’s overload thermistor has detected overheating. Causes include loose overload protector wiring, defective protector, low refrigerant (compressor running dry), oversized pipe runs without compensating refrigerant top-up, expansion valve failure, or outdoor PCB fault. Don’t keep running the unit. Compressor damage risk.

Code 14: High Pressure Switch Activated

The high pressure switch has tripped. Most common cause we see: dirty outdoor unit restricting heat dissipation. Other causes: defective high pressure switch, overcharge of refrigerant, cooling/heating overload. Clean the outdoor unit first. See Note 3 (overload causes) below.

Code 15: Low Pressure Switch Activated

The low pressure switch has tripped. Usually means refrigerant shortage. Other possible causes: defective low pressure switch, expansion valve failure during heating, outdoor PCB fault. Refrigerant leak diagnosis required. Just topping up gas without finding the leak is a waste of money.

Code 16: Overload Protection in Cooling Mode

The system is overloading during cooling. Common causes in Singapore (Note 3 from Hitachi’s documentation):

Excessive refrigerant (someone overtopped during previous service)
Outdoor ambient temperature too high (rare in Singapore unless installation traps heat)
Outdoor air inlet/outlet short-circuited (mounted too close to a wall)
Dirty outdoor condenser
Slow outdoor fan motor
Blocked or broken outdoor fan
Blocked air inlet/outlet
Failed expansion valve or capillary

Code 17: Discharge Temperature Sensor Fault

The thermistor measuring discharge pipe temperature has failed. Cheap fix.

Code 18: AC Voltage Abnormal

The unit detected AC supply voltage above 275V or below 160V. Singapore’s normal supply is 230V. Voltage out of range is usually a supply problem, not the aircon. Check with an electrician. Sometimes it’s the driver board’s voltage sampling circuit that’s faulty.

Code 19: Suction Temperature Sensor Fault

The thermistor on the suction line has failed. Same fix pattern as other sensor codes.

Code 22: Defrosting Sensor Fault

The defrost sensor has failed. Less relevant for Singapore where defrost cycles rarely run, but the sensor still needs to function for the unit’s logic.

IPM and Outdoor Fan Faults (Codes 45-49)

Code 45: IPM (Intelligent Power Module) Fault

The IPM in the inverter drive has detected a fault. This is a serious electrical issue and can have many root causes. Hitachi’s documentation recommends checking the driver board fault LED for a sub-code that identifies the specific issue (we cover common sub-codes below). Diagnosis required. Often results in inverter PCB replacement ($300 to $600).

Code 46: IPM and Control Board Communication Fault

The control board and IPM driver board can’t communicate. Causes: loose or failed cable between the two boards, failed driver board, or failed control board. Diagnosis required.

Code 47: Discharge Temperature Too High

The discharge pipe temperature is dangerously high. Common cause: low refrigerant (the compressor is running with insufficient gas to absorb heat). Other causes: oversized pipe run without refrigerant top-up, throttling device failure, or extreme outdoor ambient temperature. Pressure test required. If it’s a slow leak, find and repair before adding gas.

Code 48: Outdoor Upper DC Fan Motor Fault

The upper outdoor fan motor (on dual-fan models) has failed or has wiring issues. Sometimes the fan is mechanically blocked by debris. Visual inspection first.

Code 49: Outdoor Lower DC Fan Motor Fault

Same as Code 48 but for the lower outdoor fan. Same diagnosis pattern.

Indoor Unit Faults (Codes 51-83)

Code 51: Drainage Protection

The drain pan’s water level switch detected water buildup. Causes: blocked drain hose, drain hose installed too high, failed water pump, failed level switch, or failed control board. Common Hitachi issue in Singapore. A proper drain pipe vacuum during servicing usually clears Code 51 immediately. If the drain pump is failing, that needs replacement. See our water leak guide.

Code 64: Indoor and Outdoor Communication Fault

Similar to Code 7 but displayed from the indoor side. Same diagnosis: check power, cable connections, and both PCBs.

Code 72: Indoor Fan Motor Fault

The indoor fan motor isn’t running or isn’t responding correctly. Causes: loose motor cable, damaged cable, failed motor, failed indoor PCB, or the fan blade is mechanically blocked. Fan motor replacement runs $200 to $350.

Code 73: Indoor EEPROM Data 1 Fault

The indoor unit’s EEPROM has data corruption. Same fix pattern as Code 4 on the outdoor side. Replace the EEPROM component or the indoor control board.

Code 74: Indoor EEPROM Data 2 Error

The EEPROM data in the MCU is corrupted. The unit can still run but user-set functions (timer settings, custom modes) won’t be saved. Reset the EE data in MCU.

Code 81: Indoor Ambient Temperature Sensor Fault

The room temperature sensor has failed. The unit can’t accurately read room temperature. Cheap fix.

Code 83: Evaporator Middle Temperature Sensor Fault

The thermistor on the evaporator coil has failed. Cheap fix.

System Protection Faults (Codes 91-97)

Code 91: IPM Board Overheating

The IPM (inverter board) is overheating and the unit has shut down to prevent damage. Causes: high outdoor ambient temperature, slow AC fan motor (capacitor issue), poor installation with restricted airflow around the outdoor unit, or low power supply forcing the inverter to work harder. Check the outdoor fan capacitor and ensure proper ventilation.

Code 96: Refrigerant Shortage

The unit has detected low refrigerant. Discharge the existing refrigerant and recharge to the correct amount per the unit’s rating label. Important: if refrigerant is low, there’s a leak somewhere. Find and repair the leak before recharging, otherwise the gas will be gone again within months.

Code 97: 4-Way Valve Commutation Failure

The 4-way reversing valve (for switching between cool and heat) isn’t operating correctly. Causes: loose coil wiring, failed coil, failed valve itself, or failed driver board. Less common in Singapore where cool-only operation dominates.

Communication Faults (FE, ER)

FE: Wired Remote Controller Communication Fault

The wired remote can’t communicate with the indoor control board. Displayed on the wired remote. Causes: loose wiring between remote and control board, wrong wire sequence, damaged wiring, failed wired controller, or failed indoor control board. Check the wiring first.

ER: Display Board Communication Fault

The display board on the indoor unit can’t communicate with the main control board. Same diagnosis pattern as FE.

Driver Board Sub-Codes (When Code 45 Is Active)

When Code 45 (IPM fault) is showing, the driver board’s own LED flashes a sub-code identifying the specific drive issue:

Sub-code 1: Inverter DC voltage overload (check power supply, replace driver board)
Sub-code 2: Inverter DC low voltage
Sub-code 3: Inverter AC current overload
Sub-code 4: Compressor out-of-step detection (often compressor failure)
Sub-code 5-6: Compressor phase loss detection
Sub-code 7-8: Inverter IPM fault (system overload or compressor wear)
Sub-code 11: PFC power detection failure (unstable power supply)
Sub-code 12: PFC overload current (system overload or PFC fault)
Sub-code 22: Communication failure between driver board and control board
Sub-code 26-30: Various current control errors (system overload or driver fault)

If you see Code 45 plus a sub-code, send both to us via WhatsApp. The combination tells us exactly what’s failing and what part to bring.

What to Do When You See a Hitachi Fault Code

Note the exact code number from the remote or LED pattern.
Check the severity using the quick reference table above.
For Medium severity codes: book a service within the next few days. The unit may still work but is degraded.
For High severity codes: switch the aircon off and call a technician. Compressor and inverter damage risk if you continue.
For Code 51 (drainage): stop using the unit until cleared, otherwise water may overflow inside your home.
For communication errors (Code 7, 64, FE, ER): first verify the outdoor unit power and check terminal connections.
WhatsApp +65 8818 5781 with a photo of the fault code or video of the LED pattern. We can usually identify the cause before sending a team.

How Much Does Fixing a Hitachi Fault Code Cost in Singapore?

Lion City Aircon pricing across Singapore (HDB, condo, landed, same rate):

Diagnostic visit: $35 to $50 per unit
Drain pipe vacuum (Code 51): from $90 per unit
Chemical wash (for Code 5 from dirty coils): from $90 per unit
Thermistor replacement (Codes 1, 2, 17, 19, 22, 81, 83): from $130 (parts and labour)
EEPROM reset or replacement (Codes 4, 73, 74): from $130
Capacitor replacement: from $130
Fan motor replacement (Codes 48, 49, 72): $200 to $350
Indoor PCB replacement: $250 to $450
Outdoor PCB or driver board replacement (Codes 45, 46): $300 to $600
Gas leak repair plus recharge (Codes 13, 15, 47, 96): from $180
Compressor replacement (Codes 3, 13): from $750
Expansion valve replacement: $300 to $500

If you’re on our annual maintenance contract, diagnostic visits are free and most thermistor, capacitor, and drainage fixes are included between scheduled visits.

Frequently Asked Questions About Hitachi Fault Codes

What’s the most common Hitachi fault code in Singapore?

Code 7 / 64 (indoor-outdoor communication) is the most common, followed by Code 51 (drainage), Code 5 (freezing protection from dirty filters), and Code 14 (high pressure from dirty outdoor unit). All four are diagnosable in a single visit.

Why does Hitachi use numbers instead of letters for error codes?

Hitachi’s residential and inverter aircons use a numeric system inherited from their commercial control architecture. Numbers are easier for technicians to call out over phone or radio. Some newer Hitachi models with LCD wired controllers display more descriptive codes alongside the numbers.

Can I clear a Hitachi fault code by switching off the aircon?

Communication codes (Code 7, 64) sometimes clear with a full power reset if the cause was a transient power dip. Sensor and mechanical codes won’t clear because the underlying issue is physical. Compressor protection codes (Code 13) need the root cause fixed before they’ll clear.

My Hitachi’s LEDs are flashing but I don’t see a code. How do I read it?

Count the flashes between pauses. Each flash corresponds to a digit. For example, three flashes, pause, five flashes equals Code 35. If you have a wired remote, use its check function. If you can’t decode the flash pattern, send us a video on WhatsApp.

What is Code 45 and why is it so serious?

Code 45 indicates an IPM (Intelligent Power Module) fault on the inverter drive. The IPM converts incoming AC power to the variable DC the compressor needs. When it fails, the unit can’t drive the compressor properly. The fault often comes with a sub-code on the driver board’s LED that pinpoints the specific issue (overload, compressor fault, power supply issue, etc.). Inverter PCB replacement typically runs $300 to $600.

Should I try to fix Hitachi codes myself?

Filter cleaning, drain pipe checks, basic power resets, and visual inspection of cable connections are safe DIY. Anything involving refrigerant (Codes 13, 15, 47, 96), inverter components (Codes 45, 46, 91), or PCB replacement needs a licensed technician. Refrigerant handling is regulated in Singapore.

How long does fixing a Hitachi fault code take?

Most diagnoses take 30 to 45 minutes. Sensor and EEPROM replacements add 30 minutes. Fan motor or PCB replacements take 60 to 90 minutes. Compressor replacement takes 2 to 3 hours. We carry common parts on the truck, so most fixes are complete in a single visit.

Will running my Hitachi with a fault code damage it?

Depends on the code. Medium severity codes won’t cause additional damage short-term. High severity codes (Codes 3, 13, 14, 15, 45, 47, 91, 96) risk serious component damage if ignored. When in doubt, switch off and ask us.

Are Hitachi fault codes the same across all models in Singapore?

The core numeric code system is consistent across Hitachi inverter residential splits and SkyCirc commercial models. Some commercial models have additional codes specific to multi-zone systems. Standard residential split aircons in Singapore use the codes covered above.

Get Your Hitachi Aircon Fixed Today

Most Hitachi fault codes are diagnosable in a single visit. The longer you wait with an active fault, the more likely cascading damage develops, especially with compressor protection codes (Codes 13, 47) and inverter codes (Codes 45, 91).

WhatsApp +65 8818 5781 with a photo or video of the fault code and your outdoor unit nameplate. We diagnose remotely where possible and dispatch a team. Same-day service in most cases across Singapore. 22,000+ jobs done since 2016, 5.0★ across 1,500+ Google reviews, BizSafe Level 3 certified.

No scare tactics. No upselling. If your fix is a $130 thermistor, we’ll tell you that and price it accordingly. If it’s a serious inverter or compressor issue, we’ll show you what we found and give you honest repair-versus-replace numbers before doing anything.

WhatsApp Lion City Aircon · Call +65 8818 5781 · Book online