Mitsubishi Heavy Industries Aircon Blinking Light Guide
MHI units display E-prefix error codes on the panel or encode faults through LED blink patterns on older models. MHI is a separate brand from Mitsubishi Electric with a completely different code system — matching the right code to the right brand matters before anything else.
What each indicator light on an MHI indoor unit does
MHI SRK indoor units use two or three LEDs whose roles differ by model — newer display models show E-prefix codes directly, while older units rely on LED blink counting.
| LED | Color | Role |
|---|---|---|
| Operation light | Green | Running status — steady when cooling, blinks to signal faults |
| Timer light | Orange | Timer status — also flashes during certain fault conditions |
| Power or standby light | Green or red (varies by model) | Indicates unit has mains power (not present on all models) |
SRK indoor unit LEDs and display models
Most MHI wall-mounted units in Singapore (SRK series, including SRK20 to SRK71 models) have two to three LEDs on the front panel. The operation light (green) shows running status. A timer light (orange) indicates timer function or flashes during faults. Some models include a separate power or standby indicator.
Newer MHI units with a display panel show E-prefix error codes directly (E1, E3, E6, etc.). Older SRK models without a display use LED blink counting — the operation and timer lights flash in a pattern that encodes the fault number.
MHI is not Mitsubishi Electric
MHI is a completely separate brand from Mitsubishi Electric (Starmex). The two brands use different error code systems, different parts, and different PCB designs. An E6 on an MHI unit means something different from an error on a Mitsubishi Electric unit. Check the model sticker for SRK model numbers to confirm you have an MHI unit before using this guide.
Normal MHI indicator light behavior — not a fault
Before looking up codes, rule out the patterns that are part of normal operation. These are commonly mistaken for faults on MHI units.
A steady green operation light means the unit is running normally. A slow green blink means standby — powered and waiting for a remote command. The operation light staying on with no airflow for a few minutes after startup is normal compressor protection delay.
On inverter MHI models, the operation light may pulse slowly during the ramp-up period as the compressor adjusts speed, then settle once the unit reaches the set temperature.
| Pattern | What it means |
|---|---|
| Steady green operation light | Unit running normally in cooling mode |
| Slow green blink (operation light) | Standby — powered on, waiting for remote command |
| Green light on, no airflow for a few minutes | Compressor protection delay after power cycle — normal |
| Slow pulse on inverter models | Compressor ramp-up — stops once set temperature is reached |
How MHI encodes error codes through LED blinks and display
MHI surfaces E-prefix codes either on the display panel directly or through a two-LED blink pattern on older models without a screen.
Display models: E-code shown on panel
On units with a display panel, MHI shows E-prefix codes directly (E1, E3, E6, E9, E32, etc.). The E is followed by one or two digits. Some models show the code on the indoor unit panel, while others show it on the wireless remote when the unit enters fault mode.
LED blink models: tens and units digit
On older models without a display, the operation and timer lights blink in a counted pattern. The operation light encodes the tens digit and the timer light encodes the units digit. For example, 0 blinks on operation and 6 blinks on timer means E6.
Error codes persist in memory after power is removed. After a repair, the technician clears stored codes using the remote control or by shorting specific pins on the indoor PCB test connector.
Once you have the code
MHI uses a single E-prefix code series across all fault types. Single-digit E codes (E1 to E9) cover communication and sensor faults. Two-digit E codes (E10 to E39) cover compressor protection, inverter module faults, and system-level protection triggers. Once you have your E code, the full MHI error code lookup table is on the dedicated Mitsubishi Heavy Industries error code page.
How to tell MHI apart from Mitsubishi Electric
MHI and Mitsubishi Electric are different companies with different code systems — confirming which brand you have before looking up any fault code is essential.
Brand identifiers on the model sticker
Confusing MHI with Mitsubishi Electric is one of the most common mistakes when looking up error codes, and using the wrong brand's fault table leads to incorrect diagnosis. MHI units are branded "Mitsubishi Heavy Industries" on the model sticker and use SRK (indoor) and SRC (outdoor) model numbers. Mitsubishi Electric units are branded "Mitsubishi Electric" and use MSY, MSZ, or MXY model numbers (Starmex branding in Singapore).
Error code format differences
Error code formats also differ. MHI uses E-prefix codes (E1, E6, E32). Mitsubishi Electric uses a different alphanumeric system with P-codes, U-codes, and E-codes that map to its own fault categories. If the model sticker says SRK, use this guide. If it says MSY, MSZ, or Starmex, use the Mitsubishi Electric guide instead.
How multi-split MHI systems display faults differently
On MHI multi-split systems, each indoor unit reports its own fault code independently — whether all units blink or just one determines where the fault is most likely located.
All units blink vs one unit blinks
On an MHI multi-split system (SCM outdoor unit with multiple SRK indoor units), each indoor unit has its own display or LED set. The error code appears on the specific indoor unit experiencing the fault.
If all indoor units show the same code or stop cooling at the same time, the outdoor unit is the likely source. Common shared-fault codes include E1 (communication), E14 (high pressure), and E32 (low pressure from refrigerant loss).
E31 mismatch and per-unit fault checking
E31 (model mismatch) is specific to multi-split configurations. It triggers when an indoor unit is connected to an incompatible outdoor unit — usually after a partial replacement where only one component was changed.
For multi-split troubleshooting, check each indoor unit individually. If only one unit shows a code while the others run normally, the fault is isolated to that unit or its wiring connection to the outdoor unit.
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