Mitsubishi Heavy Industries aircons are the quiet workhorses of Singapore. Plenty of flats and shops run SRK wall units and SCM multi split systems, and because the brand is less common than its famous cousin, finding accurate error code information is harder than it should be. We install and service MHI systems, so here is our working guide, the same knowledge our technicians use on jobs.
First, make sure you actually have a Mitsubishi Heavy unit. MHI and Mitsubishi Electric are two different companies with completely different diagnostic systems, something we explained in our Mitsubishi Electric vs Mitsubishi Heavy comparison. If your indoor unit model starts with MSY or MSXY, you have Mitsubishi Electric, and you want our Mitsubishi Electric error codes guide instead. If it starts with SRK, stay right here.
How MHI units tell you something is wrong
MHI residential units communicate faults two ways. If you have a wired controller or check the unit with a remote in service mode, you get an E number code. Without that, the indoor unit signals through blink patterns on the RUN and TIMER lights, and the pattern corresponds to an error code. The exact blink sequences vary between models, which is why we always confirm against the specific model on site. If your lights are blinking and you cannot decode them, take a 10 second video and WhatsApp it to us at +65 8818 5781, our technicians read these daily.
The MHI error codes we see most in Singapore
E5: indoor to outdoor communication error. The two units have stopped talking. Sometimes a power cycle clears it, switch off at the breaker for five minutes. If it returns, the interconnection cabling or a control board needs professional attention.
E6: indoor heat exchanger sensor fault. A sensor problem, not a cooling problem, but the unit may refuse to run until it is replaced.
E7: room temperature sensor fault. Same family as E6. Sensor replacements are quick, inexpensive repairs when done by someone with the right part.
E9: drain trouble. The float switch has detected water where it should not be. This is the classic clogged drainage symptom, and it usually means the unit needs proper drainage clearing, not just a reset. Continuing to run it risks water on your floor.
E16: indoor fan motor fault. The blower is not spinning at the speed the board expects. Sometimes it is a failing motor, sometimes years of dirt physically dragging the blower wheel down.
E35: outdoor heat exchanger overheating during cooling. Very often a filthy condenser coil that cannot shed heat, especially for outdoor units in hot, enclosed ledges. A proper condenser cleaning fixes many E35 cases.
E36: discharge pipe temperature too high. The compressor is running hotter than it should, frequently connected to low refrigerant or airflow problems. Stop running the unit and get it checked, this one damages compressors when ignored.
E40: high pressure protection. The system pressure exceeded safe limits. Common culprits: blocked condenser, service valves not fully open after recent work, or overcharged gas. Professional diagnosis needed.
E42: current cut, compressor overcurrent. The system shut down to protect the compressor from drawing too much current. This is one of the most common serious MHI codes we attend. Causes range from a struggling compressor to voltage issues to a blocked outdoor unit.
E57: refrigerant shortage or closed service valve. The system detects it is not moving enough refrigerant. If your aircon also cools poorly, a leak is likely. As we always tell customers, topping up gas without finding the leak is renting cold air, find and fix the leak first.
E58: compressor current safe stop. A protective stop related to compressor load. Related territory to E42, and equally worth a professional look rather than repeated resets.
E59: compressor startup failure. The compressor tried to start and could not. On older systems this can signal a compressor reaching end of life, but we have also seen E59 caused by failing capacitors and boards, which cost far less. Diagnose before you replace anything.
E60: compressor rotor lock. The compressor motor cannot turn. Serious, but again, diagnosis first, replacement talk second.
Before you call anyone
Two safe things worth trying once: switch the unit off at the breaker, wait five minutes, and restart, transient faults clear this way. And check your filters and outdoor unit airflow, a choked system triggers more protection codes than any actual component failure. If the code returns after a power cycle, stop resetting and get it looked at, protection codes exist to prevent expensive damage.
The honest note about MHI codes
MHI uses different code tables across model generations, cassette and ducted commercial units (FDT, FDUM series) have their own set, and blink patterns differ by model. Treat this guide, and any online guide, as a starting point rather than gospel. The definitive answer comes from your unit’s service documentation, or from a technician who works on MHI regularly. All seven of our teams do.
MHI showing an error code right now?
WhatsApp +65 8818 5781 with your model number (on the sticker under the indoor unit’s front panel) and the code or a video of the blinking lights. We will tell you honestly whether it is a five minute fix, a repair worth doing, or, on an old system, whether the money is better put toward a new 5-tick system. Our repair service covers all MHI residential systems, and with 1,800+ Google reviews you can check how we handle these jobs before you call.
Error code guides for other aircon brands
We keep a full library of error code guides written by our technicians. Find your brand here: EuropAce | Sharp | Hisense | TCL | Gree | Midea | Haier | Samsung | LG | Fujitsu | York | Toshiba | Sanyo | Carrier | Hitachi | Panasonic | Mitsubishi Electric | Daikin.
