Outdoor Control System Memory Error
Mitsubishi Electric · Mitsubishi MSZ-FH06-18NA Heat Pump System
What does 7-time blink 2.5-second OFF mean?
This error indicates that the inverter P.C. board or the outdoor electronic control P.C. board cannot properly read data from its nonvolatile memory. This signifies a corrupted or inaccessible memory on the outdoor control board, critical for compressor control and overall unit coordination. If this issue is not resolved, the outdoor unit will be unable to operate, making the entire system non-functional.
Common Causes
- Corruption of the nonvolatile memory (EEPROM, Flash) on the inverter P.C. board or outdoor control P.C. board due to unstable power supply or voltage spikes.
- Electrostatic discharge (ESD) or transient overvoltage damaging the memory chip or its associated data bus.
- Internal hardware defect on the P.C. board (e.g., faulty memory component, poor solder joint).
- Firmware update failure or interruption causing an incomplete or corrupted memory write.
- Prolonged exposure to harsh environmental conditions (e.g., extreme temperature, humidity) leading to component degradation.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Disconnect main power to the outdoor unit for a minimum of 5 minutes to allow for a complete power cycle and memory refresh.
- 2
Verify stable DC power supply voltages (e.g., 5VDC, 12VDC, 15VDC) to the control sections of the outdoor P.C. board and inverter P.C. board using a multimeter.
- 3
Check for any loose or corroded connections for any removable memory modules (e.g., DIP switches, configuration jumpers) on the outdoor control P.C. board.
- 4
If applicable, attempt to re-initialize the unit parameters or re-load the default firmware using the service tool or built-in service mode (refer to the service manual).
- 5
Inspect both the inverter P.C. board and the outdoor electronic control P.C. board for any visible signs of damage (e.g., burnt components, electrolyte leakage from capacitors).
- 6
If the error persists, replace the outdoor electronic control P.C. board or the inverter P.C. board, whichever is determined to be the primary control unit with the faulty memory.