BoilerFaultCodesIdeal 89 Fault Code
The Ideal 89 fault code means: your boiler's hot water sensor has stopped working, meaning it cannot accurately tell the system the temperature of the water, so it has shut down to prevent damage.. It appears on 5 Ideal models in our database.
Technical description: ALTERNATING ‘F’ AND ‘0’ - NO WATER FLOW THERMISTOR FAULT
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like 89: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Ideal models that show the 89 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 89 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026