The most common phone call we get on a hot Singapore afternoon goes like this. The aircon stopped cooling about twenty minutes ago. There is a green light blinking on the indoor unit. The homeowner has switched it off and on three times. The light keeps blinking. They want to know if the unit is dying and how much a new one costs.
The answer almost always starts with: take a photo of the blinking pattern, send it to us on WhatsApp, and we will tell you what is wrong in five minutes. About 30% of the time the fix is something the homeowner can do without a technician. The other 70% need a service visit, but knowing the actual fault before the technician arrives saves time, money, and the panic-buying decision to replace a unit that needs a $90 capacitor.
This article is the reference we wish more Singapore homeowners had. Complete Daikin and Mitsubishi Electric Starmex error code lists, what each code actually means, what the repair costs, and which faults are safe to try fixing yourself before calling someone.
How to Read the Code on Your Unit
The two brands use different diagnostic methods. Both are simple once you know the procedure.
Daikin — Use the Remote
Daikin units do not display the error code on the indoor unit. The code comes from the remote.
Stand in front of the indoor unit so the remote signal reaches the receiver. Press and hold the CANCEL button for about 5 seconds. The remote screen flashes “00”. Press CANCEL repeatedly to cycle through codes (A0, A1, A3, A5, A6, C4, C5, C7, C9, E0, E1, E3 and so on). When the code on the remote matches the unit’s actual fault, the indoor unit emits a long continuous beep. Write that code down. That is your fault.
If you do not have your original Daikin remote, the universal remote that came with most third-party purchases does not run the diagnostic mode. You will need to buy a replacement original Daikin remote (around $45 to $80) or call a technician to bring his.
Mitsubishi Electric Starmex — Count the Blinks
Mitsubishi residential units (FN, FJ, GP, GE series) display the fault through blink patterns on the indoor unit indicator LED. The Operation Lamp blinks a specific number of times, pauses for about two seconds, then repeats.
Stand close enough to see the LED clearly. Watch for one complete cycle. Count the blinks between pauses. A pattern of blink-blink-blink, pause, blink-blink-blink means 3 blinks. Note whether it is the Operation Lamp blinking, the Timer Lamp blinking, or both. Some faults show on one LED, others on both.
If the indicator is solid (not blinking) and the unit will not start, check first whether the horizontal louver flap is clipped in properly. A loose louver triggers a startup block on some Starmex FN models. Push the louver firmly until it clicks. Try the unit again before assuming there is a fault.
Daikin Error Codes — Complete Reference
The codes below are what we see most often on Daikin residential split systems in Singapore. The full Daikin reference catalogue has more codes used in commercial VRV and chiller systems. The list here covers wall-split, multi-split, and cassette units for HDB and condo installations.
Indoor Unit Faults
| Code | What It Actually Means | Typical Repair Cost (2026) |
|---|---|---|
| A0 | External protection device activated (drain pump or float) | $80 to $200 |
| A1 | Indoor PCB defective | $280 to $480 |
| A3 | Drain water level abnormal (drain pan full) | $130 to $280 |
| A5 | Freeze-up protection / high pressure protection | $180 to $450 |
| A6 | Indoor fan motor locked or overloaded | $180 to $320 |
| A7 | Swing flap motor (louver) malfunction | $120 to $220 |
| A9 | Electronic expansion valve malfunction | $280 to $480 |
| AH | Air filter / dust collector abnormal | DIY clean filter, no cost |
| C4 | Indoor heat exchanger thermistor (liquid pipe) fault | $120 to $220 |
| C5 | Indoor heat exchanger thermistor (gas pipe) fault | $120 to $220 |
| C7 | Front panel position fault | DIY check, $80 if service |
| C9 | Indoor room air thermistor fault | $120 to $220 |
| CA | Discharge air thermistor abnormal | $150 to $250 |
| CJ | Remote control air thermistor abnormal | Remote replacement $45-$80 |
Outdoor Unit Faults
| Code | What It Actually Means | Typical Repair Cost (2026) |
|---|---|---|
| E0 | Outdoor protection device activated | $150 to $400 |
| E1 | Outdoor PCB defective | $380 to $680 |
| E3 | High pressure switch triggered (system overheating) | $180 to $480 |
| E4 | Low pressure switch triggered (refrigerant low or blocked) | $180 to $450 |
| E5 | Inverter compressor motor locked | $1,500 to $3,500 |
| E6 | Compressor motor start failure (often a capacitor) | $80 to $250 (capacitor) |
| E7 | Outdoor fan motor malfunction | $220 to $380 |
| E8 | Input overcurrent (electrical issue) | $180 to $450 |
| E9 | Outdoor electronic expansion valve malfunction | $280 to $480 |
| F3 | Discharge pipe temperature abnormal (often refrigerant low) | $90/kg R32 top-up + repair |
| F6 | Heat exchanger temperature abnormal | $180 to $380 |
| H6 | Position detection sensor abnormal | $250 to $450 |
| H7 | Outdoor fan motor signal abnormal | $220 to $380 |
| H8 | Compressor input current detection abnormal | $250 to $480 |
| H9 | Outdoor air thermistor abnormal | $120 to $220 |
| J3 | Discharge pipe thermistor abnormal | $150 to $250 |
| J5 | Suction pipe thermistor abnormal | $150 to $250 |
| J6 | Outdoor heat exchanger thermistor abnormal | $150 to $250 |
| L3 | Electrical box temperature abnormal | $180 to $380 |
| L4 | Inverter cooling abnormal (inverter PCB overheating) | $380 to $680 |
| L5 | Inverter compressor abnormal (DC fault, overcurrent) | $480 to $880 |
| L8 | Inverter compressor overcurrent (sustained overload) | $480 to $880 |
| L9 | Inverter compressor stall prevention | $380 to $680 |
| P3 | Electrical box thermistor abnormal | $180 to $280 |
| P4 | Inverter cooling thermistor abnormal | $180 to $280 |
Communication and System Faults
| Code | What It Actually Means | Typical Repair Cost (2026) |
|---|---|---|
| U0 | Refrigerant shortage (system has lost gas) | $90/kg R32 + leak repair |
| U1 | Reverse phase / open phase (electrical) | $80 to $250 |
| U2 | Power voltage abnormal | $80 to $250 |
| U4 | Communication error between indoor and outdoor | DIY breaker reset first |
| U5 | Communication error between remote and indoor | Remote $45-$80, or PCB |
| U7 | Communication error between outdoor units (multi-system) | $280 to $580 |
| UA | Combination error (wrong indoor/outdoor match) | $0 (config), $280 if PCB |
| UF | Refrigerant pipe / wiring mismatch (installation error) | $480+ (re-route work) |
Mitsubishi Electric Starmex Blink Pattern Reference
The blink codes for Singapore Starmex residential units follow these patterns. The Operation Lamp is the main indicator. Some faults also blink the Timer Lamp simultaneously.
| Blink Pattern | What It Actually Means | Typical Repair Cost (2026) |
|---|---|---|
| Operation Lamp 2 blinks | Indoor coil pipe temperature sensor fault | $120 to $220 |
| Operation Lamp 3 blinks | Indoor room temperature sensor fault | $120 to $220 |
| Operation Lamp 4 blinks | Indoor fan motor fault | $180 to $320 |
| Operation Lamp 5 blinks | Communication fault (indoor to outdoor) | DIY breaker reset first |
| Operation Lamp 6 blinks | Outdoor unit fault (compressor, sensor, or PCB) | $250 to $880 depending |
| Operation Lamp 7 blinks | Outdoor fan motor fault | $220 to $380 |
| Operation Lamp 8 blinks | Compressor abnormal (often start failure) | $80 to $250 (capacitor) |
| Operation Lamp 11 blinks | Pressure switch triggered | $180 to $450 |
| Operation Lamp 14 blinks | Discharge temperature abnormal (overheating) | $180 to $450 + gas check |
| Operation Lamp 15 blinks | Voltage / power abnormal | $80 to $280 |
| Timer Lamp 2 blinks | Indoor temperature sensor secondary fault | $120 to $220 |
| Timer Lamp 3 blinks | Indoor fan motor secondary fault | $180 to $320 |
| Timer Lamp 5 blinks | Communication secondary fault | DIY reset, then service |
| Timer Lamp 6 blinks | Outdoor major fault (compressor or PCB) | $480 to $3,500 |
| Both Lamps Continuous Slow | Indoor PCB fault | $280 to $480 |
| Both Lamps Continuous Fast | Refrigerant detection abnormal (possible leak) | $90/kg R32 + leak repair |
| Power Lamp Continuous | Indoor PCB malfunctioning | $280 to $480 |
| Rapid Flicker 12 Times | Refrigerant amount abnormal (over or under charged) | $250 to $580 |
For Starmex multi-split outdoor units (MXY-3, MXY-4, MXY-5 series), the outdoor unit also has its own diagnostic LED inside the electrical panel. Service technicians read that LED to confirm the indoor-displayed code. For homeowner diagnosis, the indoor LED count is enough to identify the fault category.
The Five Codes Singapore Homes See Most Often
Across our service callouts in the first half of 2026, five codes account for around 70% of all Daikin and Mitsubishi error code complaints. The patterns are predictable because the Singapore climate stresses certain components more than others.
The Number One: U0 (Daikin) / Continuous Fast Blink (Mitsubishi) — Refrigerant Loss
This is the most common error we diagnose. The system has lost gas, usually through a slow leak at a brazed joint or a flare connection in the outdoor unit. The unit may still produce some cooling but the temperature does not drop properly and the code eventually triggers.
The wrong fix is a gas top-up alone. The leak is still there. The refrigerant we just paid for at $90 per kilogram for R32 will be gone in 8 to 18 months. The right fix is pressure-testing the system to find the leak, repairing the joint, then refilling. The combined repair runs $280 to $580 for residential systems depending on leak location.
Top-up-only is the most common upselling pattern in the Singapore aircon market. A contractor charges $200 to $300 every year for refrigerant top-ups instead of fixing the leak once for $400 to $600 and ending the problem. We have seen customers paying for top-ups year after year without realising the underlying leak was never investigated.
The Number Two: A3 (Daikin) / P4 or P5 (Mitsubishi-related) — Drain Issues
Water leaking from the indoor unit, combined with this fault code, almost always traces to drain pipe biofilm buildup. The drain pan fills, the float switch triggers, the unit shuts down to prevent water damage.
The DIY check is removing the front cover and looking at the drain pan. If you see standing water with a brown or black biofilm coating, the drain line is clogged. Calling for a chemical wash ($110 to $130) solves the immediate problem. If the issue keeps coming back every 6 to 12 months, the root cause is the drain pipe diameter or slope being wrong from the original installation. The fix in that case is rerouting the drain pipe properly, around $250 to $400.
The Number Three: U4 (Daikin) / 5 Blinks (Mitsubishi) — Communication Error
The indoor and outdoor units lose communication. The DIY first step is switching off the main circuit breaker for 20 minutes, then switching it back on. About 40% of communication errors clear with a reset. The fault was a transient electrical glitch that locked the controller.
If the error returns within 24 hours, the cause is usually one of three things. Loose wiring at the indoor or outdoor terminal block ($80 to $150 to re-secure). A failed communication PCB on the indoor unit ($280 to $480 to replace). A signal cable damaged by rodents or physical impact, common in older HDB flats where the cable runs through ceiling voids ($150 to $400 to replace the cable section).
The Number Four: A6 (Daikin) / 4 Blinks (Mitsubishi) — Fan Motor Fault
The indoor fan motor stops spinning, spins slowly, or draws abnormal current. The fault triggers and the unit shuts down to prevent motor burnout.
In about half of A6 / 4-blink cases, the cause is mechanical interference rather than motor failure. Dust accumulation on the fan rotor, a loose front cover obstructing the fan, or insect debris (we have removed gecko nests from fan housings more than once). A thorough chemical wash often clears the fault without replacing the motor.
In the other half, the motor itself has failed — usually a worn bearing or burned-out winding after 6 to 9 years of service. Fan motor replacement runs $180 to $320 depending on the model.
The Number Five: E6 (Daikin) / 8 Blinks (Mitsubishi) — Compressor Start Failure
The compressor will not start when commanded. This sounds catastrophic but in 70% of cases the cause is a failed run capacitor, not the compressor itself.
A capacitor replacement runs $80 to $250 depending on capacitor microfarad rating and the model. The job takes about 90 minutes. The unit usually starts the moment the new capacitor is installed.
In the remaining 30%, the compressor is genuinely failing — typically after 9 to 13 years of service. Compressor replacement on a residential unit runs $1,500 to $3,500. At that price, replacement of the entire system is often the more economical choice, especially when the rest of the components are also aged.
Faults You Can Fix Yourself (Safely)
Three error conditions are genuinely safe for a homeowner to try clearing before calling a technician.
Filter blockage warnings. Daikin AH code. Switch the unit off, remove the front cover, pull out the air filters (usually two of them), wash with running water and mild detergent, dry completely, reinstall. Switch the unit back on. The code clears. Total time: 15 minutes. Cost: zero.
Communication errors after a power event. Daikin U4, Mitsubishi 5 blinks. Switch off the main aircon circuit breaker at the household DB. Wait 20 minutes. Switch back on. If the error clears, the fault was transient. If it returns, call for service.
Loose front panel or louver. Daikin C7, Mitsubishi solid indicator that will not start. Push the front panel firmly until it clicks into position. Push the horizontal louver firmly until it clicks. Try starting the unit. About 30% of the time the unit starts immediately because the safety interlock was the only issue.
Anything beyond these three needs a technician. Refrigerant work, electrical component replacement, sensor replacement, PCB replacement, and compressor work are all qualified technician jobs. NEA regulations also require licensed handling for refrigerant work and BCA registration for any electrical modification.
Stories That Did Not End Well
Three real cases from the last year illustrate why some faults are not for DIY.
A homeowner in Bishan saw an E6 code on his Daikin System 3 and watched a YouTube video about capacitor replacement. He bought a 50 microfarad capacitor from Sim Lim Tower for $12 and installed it himself with the unit still connected to mains power. He survived the shock that knocked him off the balcony onto the kitchen window ledge below. His wife called us to remove the wrong-rated capacitor (the correct one was 35 microfarad), fix the burned PCB caused by overcurrent, and complete the actual capacitor replacement. Total cost including the original ER visit: around $3,800. Could have been $180 if he had called us first.
A condo owner in Marina Bay saw a U0 code on her Daikin and tried to top up the refrigerant herself using a R32 cylinder bought from a Tuas industrial supplier. She did not know the system was R32 and overcharged it because she was reading the gauges in PSI instead of bar. The compressor failed within two days from sustained high pressure operation. Replacement compressor and full system flush: $4,200. The original leak that triggered the U0 code was a $280 repair.
A homeowner in Sengkang saw a continuous fast blink on her Mitsubishi Starmex and assumed the unit was old and ready to be replaced. She ordered a new System 3 from a contractor on Carousell for $1,950 and had it installed three days later. The old system was 7 years old with another 5 to 8 years of life in it. The fault that triggered the blinking pattern turned out to be a $140 thermistor replacement. She paid $1,950 to solve a $140 problem.
The pattern across all three is the same. Some faults look catastrophic but are actually cheap. Some faults look minor but require licensed work. Calling a technician for a $50 diagnostic visit before making any decision saves homeowners thousands across the lifecycle of their system.
What Each Repair Tier Costs in 2026
Rough pricing for the most common repairs:
Tier 1: Cleaning and reset interventions ($0 to $150). Filter wash, drain pipe flush, capacitor replacement, thermistor replacement, breaker reset, louver re-clip. These account for about 50% of our service callouts.
Tier 2: Electrical and sensor work ($150 to $500). Fan motor replacement, drain pump replacement, EEV (electronic expansion valve) replacement, contactor replacement, wiring re-termination, communication cable repair. About 30% of callouts.
Tier 3: PCB and inverter work ($280 to $880). Indoor PCB replacement, outdoor inverter PCB replacement, control board reprogramming. About 15% of callouts.
Tier 4: Compressor and major refrigerant work ($1,500 to $4,200). Compressor replacement, full refrigerant system flush, four-way valve replacement, major leak repair with multi-joint brazing. About 5% of callouts. At this tier the cost-benefit analysis often favours system replacement instead.
Diagnostic visit alone runs $50, waived if you proceed with the repair on the same visit. The diagnostic includes the error code reading, system pressure check, electrical current draw measurement, and a written quote for the recommended repair.
How to Prevent the Light From Blinking in the First Place
Three preventive habits stop most of the codes we have listed.
Service the unit every 3 to 6 months for heavily used aircons (running 8+ hours daily), every 6 to 12 months for moderate use. A proper general service catches biofilm buildup before it triggers A3 drain codes, dust accumulation before it triggers A6 fan motor codes, and gas pressure abnormalities before they trigger U0 refrigerant codes.
Schedule a chemical wash every 2 to 4 years. The chemical wash cleans internal components that general servicing cannot reach. This intervention alone extends component life by 3 to 5 years for the fan motor, drain pump, and cooling coil.
Pressure-test the refrigerant system at year 3 and year 7. A 30-minute pressure test confirms whether the brazed joints are still gas-tight or whether a slow leak is developing. Catching a leak at the joint stage costs $280 to $400 to fix. Missing the leak and paying for refrigerant top-ups every year while the leak grows costs more across 5 years and risks compressor failure from sustained undercharged operation.
For households running a service contract with us, these three preventive interventions are bundled into the contract pricing. See our aircon service contract page for residential quarterly and half-yearly contract structures.
Frequently Asked Questions
My Daikin shows U4 and I have already reset the breaker. What now?
Call for service. U4 that persists after a breaker reset usually indicates a wiring fault or PCB fault. Diagnostic visit $50, repair typically $80 to $480 depending on cause.
Can I just buy a Daikin remote on Shopee to do the diagnostic?
Original Daikin remotes work. Universal Daikin-compatible remotes from third-party sellers usually do not run the CANCEL-button diagnostic mode. Spend the $45 to $80 on an original from a Daikin Proshop or buy a service visit where the technician brings his own.
My Mitsubishi Starmex Operation Lamp is blinking 6 times. Should I switch off the breaker immediately?
Yes. 6 blinks indicates outdoor unit fault, most often compressor-related or high-pressure switch trip. Continuing to run the system risks compressor damage. Switch off the main aircon breaker and call for service the same day.
What does it cost to fix a refrigerant leak in Singapore?
Diagnostic and leak detection: $150 to $250. Joint repair (re-flare or re-braze) typically $180 to $400. Refrigerant refill at $90 per kg for R32 (typical residential system holds 1 to 2 kg) or $110 per kg for R410A. Total repair commonly $400 to $700.
My unit is 12 years old and shows E6. Worth fixing?
Depends what is actually wrong. If it is a capacitor, fix it for $80 to $250. The unit has 1 to 3 more years of life. If it is the compressor itself, replacement at $1,500 to $3,500 on a 12-year-old system rarely pays back. New installation is usually the better choice.
How do I know if my aircon is Daikin iSmile, iSmile Eco, or iSmile Eco+?
Check the model number on the indoor unit sticker (inside the front cover). iSmile models start with “FTK”. iSmile Eco starts with “FTKM”. iSmile Eco+ starts with “CTKM”. The model number is also on the outdoor unit nameplate.
How do I know which Mitsubishi Starmex generation I have?
Check the indoor unit model. MSXY-GP** is the older GP series. MSXY-FJ** is the FJ series. MSXY-FN** is the current 2nd-generation FN series. Each generation has slight differences in error code display.
Is it dangerous to keep using the aircon when there is a blinking light?
Depends on the code. Communication errors (U4, 5 blinks) are usually safe to retry. Refrigerant codes (U0, fast blink) are safe but waste electricity because the system runs without cooling properly. Compressor and high-pressure codes (E5, E6, L5, 6 blinks, 8 blinks) should not be retried because continued operation risks expensive component damage. When in doubt, switch off and call for service.
Do you charge for over-the-phone diagnosis?
No. Send a WhatsApp message to 9654 0044 with a photo of the error code on the remote (for Daikin) or a video of the blinking pattern (for Mitsubishi). We tell you what the fault is and whether it needs a service visit. Costs nothing.
Will a chemical wash clear an error code?
For codes related to drainage (A3), fan obstruction (A6 in some cases), and biofilm-induced sensor faults, yes — the chemical wash often clears the underlying cause. For electrical faults (E6, L5, U4, PCB faults), no — the chemical wash does not touch the affected components.
What is the difference between Mitsubishi Electric and Mitsubishi Heavy Industries error codes?
Different companies, different systems, different code conventions. MHI uses alphanumeric codes displayed via the remote (similar to Daikin) on most models. This article covers Mitsubishi Electric Starmex only. For MHI codes, refer to the unit’s user manual or call us with the model number for a specific code lookup.
Closing
The blinking light on your aircon is information, not a sentence. About a third of the codes you can resolve in 15 minutes with a filter wash or breaker reset. About two-thirds need a technician but the actual repair is often cheaper than the panicked instinct to replace the whole system would suggest.
The most expensive mistake we see Singapore homeowners make is acting before diagnosing. Replacing a system that needed a $140 thermistor. Topping up refrigerant for years instead of fixing a $400 leak. Calling Carousell installers who do not bother diagnosing properly and just sell a new system as the easy answer.
The cheapest decision after seeing an error code is the $50 diagnostic visit (waived against repair if you proceed). The technician reads the code, confirms the actual fault, and quotes the actual repair. You decide whether to fix or replace with the real numbers in front of you.
If you have a code blinking right now, send a WhatsApp to 9654 0044 with a photo or short video. We respond within business hours and you have an answer before deciding anything. For service bookings, call 9654 0044 or email sales@vdairconservices.com. For after-hours emergencies (compressor faults, refrigerant leaks, electrical faults), the 24-hour repair line is the same number.
VD Aircon Engineering is a BCA-registered installer and authorised service partner for Daikin, Mitsubishi Electric, and Mitsubishi Heavy Industries in Singapore. The team has diagnosed and repaired over 40,000 unit faults since 2016. Pricing in this article reflects current 2026 standard service rates and is subject to confirmation after on-site diagnosis.
We specialize in Aircon installation, repair, and service. We have all type & model of recon compressor, full set & fancoil. Our technicians are highly proficient in their respective field and repairs and fixes aircon of various brands.
