A07
Herz
Flow Temperature Sensor Fault (NTC Flow Open/Short)
Boiler display shows A07, no heating or hot water, pump may run briefly then stop
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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
Defective Herz flow NTC sensor, broken sensor wiring, poor connector contact on main PCB, water ingress into sensor pocket
How to Fix / Troubleshooting
Safety: Isolate electrical power. The flow sensor is in contact with hot water; allow cooling before removal.
- Check wiring: Locate the flow NTC on the flow pipe leaving the Herz boiler. Inspect its cable and connector for damage or corrosion.
- Reseat connector: Disconnect and reconnect the NTC plug at both the sensor and PCB ends to clear oxidation.
- Measure resistance (for skilled users): With power off, use a multimeter to measure the NTC resistance and compare with Herz temperature/resistance table. Replace if out of range.
- Replace sensor if faulty: Drain the boiler section if required, unscrew the NTC, fit a new Herz flow NTC with thermal paste if specified, and refill/bleed the system.
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Repair Difficulty
Medium
3/5
Required Part
Herz flow NTC sensor
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