F86
FAULT CODE
Glow-worm
Underfloor Heating Contact Fault
Medium Severity
Engineer Required
On Glow-worm boilers connected to underfloor heating systems, F86 indicates a fault with the underfloor heating contact or switching circuit.
Step-by-Step Fix Guide
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Step 1
Check that the underfloor heating control wiring connections at the boiler are secure
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Step 2 Engineer only
Call a Gas Safe engineer if the fault persists
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.