Technical description
Return NTC short circuit. NTC defective, short circuit in cable harness, cable/casing short cut
What causes this fault?
This fault occurs when the sensor responsible for monitoring the temperature of water coming back into the boiler develops an electrical short circuit. The most common reason is that the sensor itself has suffered an internal failure or natural wear and tear, leading it to send an incorrect signal to the main control board. In some cases, water damage or a loose connection within the internal wiring can also cause this electrical error.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.