L4
FAULT CODE
Ideal
Overheat Lockout
High Severity
Engineer Required
The boiler's safety overheat thermostat has triggered a lockout due to excessively high temperatures.
Step-by-Step Fix Guide
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Step 1
Turn off and let cool for 30 minutes
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Step 2
Check and correct system pressure
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Step 3
Bleed radiators
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Step 4
Reset once
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Step 5 Engineer only
If L4 returns, call a Gas Safe engineer
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.