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Issues with air handler fan – GreenBuildingAdvisor
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Mitsubishi SVZ ducted air handler fan won’t run after modifying function codes 25 & 27
A technician accessed the indoor unit function settings via the PAR-43MAAUB and modified:
- Function Code 25 (Fan speed Thermo-OFF Heating)
- Function Code 27 (Fan speed Thermo-OFF Cooling)
- He changed both to “Stop” (value = 2) per the official Mitsubishi M&P Series Function Settings List documentation.
After the modification, no airflow comes from the ducts anymore when I try to test ventilation mode (either low or high speed). The fan simply does not start.
The technician told me: “The system does not allow this option if I disable continuous ventilation.”
Before the change, the fan ran continuously in AUTO mode (expected for SVZ ducted units apparently)
Any help would be greatly appreciated. Thanks!