03 Fujitsu — Outdoor unit communication fault
At a glance
- Severity
- FAULT STOP
- Domain
- VRV_VRF_system
- Reference standard
- EN 378-2:2016, IEC 61000-6-2 (EMC)
- Product / context
- Outdoor unit communication error
What it means
The master outdoor unit cannot communicate with the slave outdoor units (in modular systems) or with the centralized controller. The system stops completely because the master unit cannot coordinate compressor operation and load distribution.
Probable causes
- Communication cable between outdoor units damaged or with oxidized connectors
- Communication board on master or slave unit faulty
- Electromagnetic interference from adjacent power cables
- Incorrect master/slave configuration after board replacement
- Missing or incorrect bus termination resistor
Where to start
Check the communication cable between outdoor units. Verify master/slave configuration (DIP switches or software). Check the termination resistor on the last unit of the bus. Measure the communication signal with an oscilloscope.
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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