Lockout 1 flash + LED 2 error code
Lockout 1 flash + LED 2 — Cabinet overheat safety lockout
What does Keston Celsius 25 and 25P boilers Lockout 1 flash + LED 2 mean?
One red lockout flash with diagnostic LED 2 illuminated identifies a cabinet overheat condition or operated cabinet thermal fuse.
The code identifies the condition detected by the product; it does not always identify the failed component on its own. Confirm the full code and exact model before ordering parts or attempting a reset.
The Keston Celsius 25 and 25P boilers Lockout 1 flash + LED 2 error code indicates one red lockout flash with diagnostic LED 2 illuminated identifies a cabinet overheat condition or operated cabinet thermal fuse. This guide explains what the code means, the symptoms and likely causes, the checks that are safe to make, and when to stop and arrange an authorised repair.
Symptoms you may notice
Red lockout LED flashes once every two seconds; diagnostic LED 2 is on; boiler stops.
Common causes
Cabinet thermal fuse operated; heat leakage from combustion-area joints; pump or fan run-on problem.
Before you start troubleshooting
Use the display, rating label or product menu to confirm the exact model. Similar-looking codes can have different meanings across product generations and regions.
- Record the complete code before switching the equipment off.
- Check only user-accessible controls, filters and external connections described in the manual.
- Do not open gas, refrigerant, combustion or electrical compartments.
Troubleshooting steps
Switch the appliance off and arrange an engineer visit. The casing must not be opened by the user. The combustion area, thermal fuse, joints, fan and pump run-on require professional checks.
Can you fix this error code yourself?
This fault is not intended for user repair. Do not remove covers or test internal components; record the code and contact an authorised technician.
A successful reset is not proof that the underlying issue is fixed. If Lockout 1 flash + LED 2 reappears, note when it happens and give that information to the service engineer.
Reset instructions
Only reset after the underlying condition has been checked. Where the official manual permits a reset, turn the boiler user-control knob off, wait, then turn it on again. Do not repeatedly reset a returning lockout.
Applicable products and models
Celsius 25 and 25P boilersCelsius 25; Celsius 25PLegacyWhen to contact a professional
Contact a Gas Safe registered engineer if the pattern returns, the boiler will not reset, there is evidence of overheating or leakage, or any check requires access inside the appliance.
Frequently asked questions
What does Keston Celsius 25 and 25P boilers Lockout 1 flash + LED 2 mean?
One red lockout flash with diagnostic LED 2 illuminated identifies a cabinet overheat condition or operated cabinet thermal fuse.
Can I fix Keston Celsius 25 and 25P boilers Lockout 1 flash + LED 2 myself?
This code is not classed as user-fixable. Record it and arrange authorised diagnosis rather than opening the product.
Should I reset the product after code Lockout 1 flash + LED 2?
Only reset after the underlying condition has been checked. Where the official manual permits a reset, turn the boiler user-control knob off, wait, then turn it on again. Do not repeatedly reset a returning lockout.
When should I arrange a repair?
Contact a Gas Safe registered engineer if the pattern returns, the boiler will not reset, there is evidence of overheating or leakage, or any check requires access inside the appliance.