E05
ACV
Flow Temperature Sensor Fault (NTC Open/Short)
Boiler displays E05 and will not start, often after a power cut or wiring work
Advertisements
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.
Advertisements
Possible Causes
Faulty flow NTC sensor, Damaged sensor wiring harness, Loose connector on control board, Control board input fault
How to Fix / Troubleshooting
Safety first: Isolate power before removing any covers. Sensors are low-voltage but live parts are nearby.
- Power cycle: Turn off the boiler at the isolator for 30 seconds, then turn back on. Sometimes transient faults clear.
- Check connections (visual): If you are competent and local regulations allow, remove the front panel and locate the flow NTC on the flow pipe leaving the ACV heat exchanger. Ensure its plug is firmly seated and the cable is not damaged or pinched.
- Inspect for corrosion: Look for signs of water leaks around the sensor pocket that may have corroded the connector.
- Do not bypass sensor: Never short or disconnect the NTC to force operation. If E05 persists, a technician should test the sensor resistance and replace it if out of specification.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
Flow NTC Temperature Sensor
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements