What to check, in order
- Open the radiator valves
Ideal says to make sure all the radiator valves are open.
- Check the pressure
The gauge should read 1 to 1.5 bar. If it's lower, top it up with the filling loop.
- Reset the boiler
Press the restart button.
When to call a Gas Safe engineer
If that doesn't fix it, contact Ideal, or a Gas Safe registered engineer if the boiler is out of warranty.
Quick answers
What does the Ideal L1 fault code mean?
Ideal lists L1 as flow temperature overheat or no water flow. The water in the boiler got too hot, or isn't moving through it, so it has stopped.
Can I fix Ideal L1 myself?
Easy (about 15 minutes). Start with: open the radiator valves; check the pressure; reset the boiler. If that doesn't fix it, contact Ideal, or a Gas Safe registered engineer if the boiler is out of warranty.
Is Ideal L1 worth repairing?
Worth fixing. Closed valves or low pressure cost nothing to sort. If it keeps happening, an engineer needs to find the cause.
Checked against
- Ideal Heating: what does my boiler fault code mean
- Ideal Heating: Logic Combi 24, 30 and 35 troubleshooting guide
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.