S.98 Low
Your boiler is temporarily pausing because it has noticed an unusual temperature difference between two internal sensors and is performing a self-check to ensure everything is working correctly.
Technical description: Flow return sensor check is running demand is block
Typical repair cost: £90-180 (including labour)
DIY fix possible
Check that all radiator valves are fully openEnsure your central heating system pressure is between 1.0 and 1.5 barWait up to 15 minutes for the boiler to complete its automatic recalibration
Protect yourself from future repair bills
A boiler cover plan would cover faults like S.98 — no call-out fees, no surprises.
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Parts commonly replaced
- Flow NTC sensor
- Return NTC sensor
- Pump
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