6607 Mitsubishi Electric — Indoor Unit Communication Error
At a glance
- Severity
- FAULT STOP
- Domain
- AIR_CONDITIONING_SYSTEM
- Reference standard
- EN 60335-2-40 / IEC 61000-6-2
- Product / context
- M-NET communication error (no ACK)
What it means
Communication between indoor and outdoor units is interrupted or disturbed; the system can no longer synchronize commands, feedback and safety conditions.
Probable causes
- Broken or reversed communication cable
- Oxidized connectors or unstable power supply
- Faulty indoor or outdoor control board
Where to start
Restore polarity, terminals and continuity of the bus. Avoid routing in parallel with power cables and redo any poor joints.
Full guided diagnosis in the app
The diagnostic tree for this fault has 5 guided steps with measurements, checks and resolutions. You'll find it in HVACIQ, one of the five IndexOS apps: free, works offline.
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The same fault on other brands
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- 1300 — Low Pressure Alarm / LP Lockout
- 1302 — High Pressure Alarm / HP Lockout
- 4250 — Compressor Overcurrent / Overload Protection
- 4400 — Outdoor Fan Motor Fault
- 5101 — Room Temperature Sensor Fault
- 1102 — Capacity unbalance between circuits
- 1300 — Low Pressure Alarm / Refrigerant Shortage