BoilerFaultCodesHeatline F84 Fault Code
The Heatline F84 fault code means: your boiler is confused because its temperature sensors are giving conflicting readings or are not properly connected, causing it to stop heating your home to prevent potential damage.. It appears on 8 Heatline models in our database.
Technical description: Permanent temperature difference between fl ow and return heating sensors. Inverted or disconnected fl ow and return heating temperature sensors. Defective temperature sensors
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Heatline models that show the F84 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Heatline F84 fault code information on this page is sourced and cross-checked against the official Heatline service / installation manuals for each affected model.
- Heatline CaprizPlus 28 manual (PDF)
- Heatline CaprizPlus 24a manual (PDF)
- Heatline Compact 24 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026