Ideal L1 and L3: overheat and no water flow are not the same fault

What Does Error L1 Mean?

Ideal publishes L1 as flow temperature overheat or no water flow and L3 as no water flow. For L1, Ideal says to open all radiator valves, confirm 1 to 1.5 bar, and reset. Its L3 guidance includes checking pressure and bleeding air from radiators. Record the exact code because the published wording and checks are not identical. Applies to: Ideal Logic and Logic Max boilers covered by the published fault code guidance These are Ideal Heating's published codes for its Logic and Logic Max ranges. Ideal also publishes an F-series in parallel, so an F1 on the same appliance is low pressure rather than an overheat. A letter and a number read from another manufacturer's boiler carries no relationship to these definitions. Owner-safe checks: Walk the house and open user-operated radiator valves and thermostatic heads; do not alter lockshield balancing valves. | Read the pressure gauge cold and top up to the 1 to 1.5 bar band Ideal names if it is low. | Bleed radiators that are cold at the top, then recheck the pressure afterwards. | Reset the boiler once after making a change, and observe a full heating cycle before deciding. | Note which radiators stay cold and where they are in the house before calling for service. Qualified technician: L1 or L3 returning after every valve is open, the pressure is correct, and the radiators have been bled. | An L5 code, which indicates the boiler has been reset too many times rather than diagnosing the original fault. | Any suspicion of a circulation pump fault or a blocked circuit, both of which need the casing opened. | Radiators that stay cold at the bottom, which points at debris in the system rather than at air. | Pressure that will not hold after topping up, which is a separate fault running alongside this one.