E05
Attack
Flow Temperature Sensor Fault (NTC Open/Short)
Boiler shows E05, heating or DHW does not start; temperature reading may be abnormal.
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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
Faulty flow NTC sensor on Attack primary circuit, Broken or shorted sensor wiring harness, Poor electrical connection at main PCB, Water ingress into sensor connector
How to Fix / Troubleshooting
Safety: Isolate power before removing covers. Components may be hot.
Steps:
- Visual inspection: Locate the flow temperature sensor (NTC) on the flow pipe leaving the Attack heat exchanger. Check for corrosion, leaks around the pocket, or damaged wiring.
- Check connector: Unplug the NTC connector from the PCB or wiring harness and inspect for moisture or oxidation. Dry and clean gently if needed, then reconnect firmly.
- Wiggle test: With power restored, gently move the cable while observing the temperature reading on the display (if available). Fluctuations indicate a wiring fault.
- Sensor replacement (basic): If you are competent and the sensor is easily accessible, drain the boiler section if required, unscrew the NTC, and replace it with a genuine Attack flow NTC sensor, using new sealing washers or O‑rings.
Note: If you are not comfortable draining the boiler or working with electrical connectors, contact an Attack service technician.
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Repair Difficulty
Medium
3/5
Required Part
Flow NTC Temperature Sensor
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