Ideal boiler fault codes explained: F1, F2, L2, F3 and what to do
- Checked September 2026
- 5 min read
- By PROS AI editorial team
Quick answer
The short version, before the detail.
On an Ideal Logic, Vogue or similar boiler the display flashes a letter and a number: F1 means the water pressure is too low and needs topping up to 1 to 1.5 bar, F2 and L2 both mean flame loss or ignition lockout, usually a gas supply or condensate problem, and F3 is a fan fault. A homeowner may top up the pressure, check the gas, thaw the condensate pipe and reset once. Everything else is Gas Safe work.
What is the likely cause?
One code per item, most common first, in Ideal Heating's own wording from its fault code FAQs.
F1 (low water pressure): Ideal says "water pressure is too low in the system and will require topping up to between 1 and 1.5 BAR".
The usual cause is that pressure has drifted down over months, or dropped after bleeding radiators; if it keeps dropping there is a leak. The one safe thing: read the gauge on the front of the boiler and top up through the filling loop to 1 to 1.5 bar, then reset. If you are topping up more than once or twice a year, Ideal says "it may indicate a water leak"; see boiler losing pressure.
F2 (flame loss or ignition lockout): the burner did not light, or the flame went out.
Ideal's checks are all about gas: reset the boiler, check a prepayment gas meter has credit, check that other gas appliances in the home are working, and check "that the yellow gas isolation valve under the boiler hasn't been turned off", which is on when its handle points along the pipe. The one safe thing is exactly that list, then one reset. If F2 persists, Ideal asks you to contact them quoting the code; the ignition electrode, gas valve and flue are engineer parts.
L2 (flame loss or ignition lockout): the same fault as F2 shown on a different display.
Ideal adds one more check for L2: whether the condensate pipe is blocked. If the boiler makes a gurgling noise while trying to fire, "contact your installer as there may be a blockage". In a freeze that blockage is ice on the outside pipe, and thawing it is the one safe thing a homeowner can do, see frozen condensate pipe.
F3 (fan fault): the fan pushes the flue gases out and the boiler will not light without it.
Ideal's advice is short: "Reset the boiler. If this does not fix the problem, please contact us quoting error code F3 as this will require a visit from an engineer." The one safe thing is that single reset.
Two neighbours worth knowing: L1 is flow temperature overheat or no water flow; Ideal's checks are that the radiator valves are open, the pressure is 1 to 1.5 bar, then reset. F4 and F5 are the flow and return thermistors, and L6 is a false flame lockout: reset once, and if the code returns it is an engineer visit.
What can I safely check myself?
Everything here is done from the display, the gauge, the filling loop and the outside wall.
- Note the code, the gauge reading and the model on the front of the boiler.
- Reset once. On the older Ideal range hold the mode dial in the reset position for three seconds; on a Logic+ or Vogue press the reset button under the display or use the menu. Wait two to three minutes. If the same code returns, stop there.
- Pressure, for F1 and L1. Cold, the gauge should read between 1 and 1.5 bar. Open the filling loop slowly, watch the needle, stop at about 1.2 bar and close both valves fully. Do not go past 1.5 bar; the pressure rises on its own when the heating runs.
- Gas, for F2 and L2. Light a hob or check another gas appliance, top up a prepayment gas meter, and look at the yellow isolation valve under the boiler: the handle should point along the pipe, not across it.
- Condensate pipe, for L2 with a gurgling noise, or any lockout in a freeze. Find the white plastic pipe outside and warm it with a hot water bottle or warm water poured along it. Ideal's wording is "tepid water" and "do not use boiling water". Only from the ground; if the pipe is at height, leave it for the engineer. Then reset once.
- Controls and power. If the display is dark, check the fused spur, the timer and the thermostat, as in boiler not firing up after summer. If the heating works but the taps run cold, that is usually a diverter valve rather than a code, see no hot water but heating works.
Do not open the casing, and do not touch the fan, the gas valve or any wiring.
When do I stop and call an engineer?
- If you smell gas, leave the property, do not switch anything on or off, and call the National Gas emergency line on 0800 111 999 from outside.
- If water is dripping near the fused spur, sockets or the consumer unit, switch off at the main switch only if it is dry and safe to reach.
- Stop if the same code returns after one reset, if F3 appears at all, if F1 comes back within days of a top-up, if F2 or L2 shows with the gas on and the condensate pipe clear, or if the boiler gurgles and the pipe is not frozen. Those are a fan, a leak, an ignition part or a blocked condensate trap, and the trap is behind the casing.
- Anything behind the casing is gas work for a Gas Safe registered engineer. Check the seven-digit number on the engineer's ID card at gassaferegister.co.uk, or text Gas and the number to 85080.
What does it cost in London?
A weekday call-out with diagnosis in London is £60 to £125, often waived if the repair goes ahead, and labour is £80 to £140 an hour. A pressure fault behind a repeating F1, meaning the expansion vessel or a valve, is £120 to £280 with the part. A fan behind F3 is £200 to £420, a pump £180 to £420 and a circuit board £290 to £650; most repairs, including the ignition parts behind F2 and L2, land between £150 and £400. Out of hours the first hour is £140 to £260.