F23
MTU Onsite Energy
Analog Sensor Supply Failure
Controller displays F23 – Sensor supply voltage fault
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Blown sensor supply fuse, Shorted sensor wiring, Failed controller power supply, Overloaded 24 VDC auxiliary supply
How to Fix / Troubleshooting
Safety first: De-energize the control panel before replacing fuses or working on wiring.
- Check controller diagnostics: Many MTU controllers display sensor supply voltage. Confirm it is out of range.
- Inspect fuses: Locate the sensor supply fuse or breaker in the control panel and test/replace if blown.
- Look for shorts: Disconnect sensor circuits one by one to identify any wiring or device that is shorting the supply.
- Power supply test: Measure the 24 VDC auxiliary supply output. If low or unstable, replace the power supply module.
- Re-enable circuits: After repairs, reconnect sensors, clear the F23 alarm, and verify normal readings.
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Repair Difficulty
Hard
4/5
Required Part
24 VDC Power Supply Module
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