F39
FAULT CODE
Glow-worm
Outdoor Temp Sensor — Freeze Warning
Medium Severity
DIY Check Possible
The outdoor sensor has detected a temperature near freezing. Frost protection may be active.
Cold Weather Note
This is a normal winter status. The boiler runs brief cycles to prevent the system from freezing.
Step-by-Step Fix Guide
-
Step 1
No action needed — the boiler may run frost protection cycles
-
Step 2
This is normal operation in cold weather
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.