Hob showing H, L, F or U400: what it means and how to reset

Read the glass before you touch anything

A hob is the one appliance designed to leave a surface at several hundred degrees with nothing visibly on. Everything else here follows from that. Before you work out whether a letter is a fault, assume the glass is hot, keep your hands off the zones, and use the controls at the front only.

H, or h, is residual heat. Hotpoint publish the threshold: the indicator stays lit until the glass is below 60°C, and on a zone that has been on high that can be twenty minutes or more. Lamona publish the warning that contradicts what everyone assumes: the zone may still be hot when the letter no longer lights up. Beko add the case people miss — after a power cut, or after somebody switched the hob off at the wall while a zone was hot, the indicator does not light at all and gives no warning. A letter that stays lit on a hob that is genuinely cold to the touch is a sensor reading wrongly, and that is a service call. A faint buzz or hum while cooking on induction is normal, and Beko say so.

The letters that are the hob working

Pan detection. A zone that flashes and will not heat usually cannot find your pan. Induction needs a ferrous base, big enough for the zone and flat against the glass. AEG's F does two jobs: flashing, it is the pan; steady, on a newly installed hob, AEG ask for the installation to be checked rather than the cookware. Beko use E 27 and E 47 for the same message. Rangemaster's E3 comes with a published test — take the pan off, wait thirty seconds for it to reset, then switch the empty zone on; if the code appears with no pan present that is Rangemaster's own threshold for the hob being at fault, and otherwise it is the pan. The universal check is a fridge magnet on the base of the pan. If it does not grip firmly, that pan will never work on induction and nothing is wrong with the hob. A pan that rocks on a flat worktop has a warped base and only touches the glass at the rim. On a Bosch or Neff hob, the cookware test in the basic settings returns a digit: zero means unsuitable, one means slower than expected, two means correct — and those digits are not fault codes. AEG's order is deliberate: dry the glass and the base, put the pan on the zone first, then turn the zone on, and expect the zone to switch itself off after two minutes with an unsuitable pan on it.

Locks. L on an AEG is one of two locks. The Lock function clears with a second touch of the key and keeps your setting. The Child Safety lock re-arms every time you switch the hob off, which is why a hob seems to lock itself; to turn it off properly, activate the hob without setting a heat level, hold the key for four seconds and look for a zero on the display. To use the hob once without turning it off, activate it, wait for the L, hold the key for four seconds and set a heat within ten seconds. A wet panel can register touches you did not make, including on the lock key, so wipe and dry it first.

Something on the controls. Beko's FF means the panel is being touched — a hand, a pan pushed too far forward, a lid, a cloth, a spill, or steam from a hard boil. Neff's F5 means hot cookware is sitting too close to the control panel; move it with a cloth, because the pan is hot enough to have heated the glass through, and if no power level was showing touch any button to bring the zone back. The fix for both is where you put things: keep the front strip of glass clear and put large pans on the back zones.

Power sharing. An AEG display flashing between two numbers is not a malfunction. Two zones on one side share a supply; the higher number is what you asked for and the lower is what the hob can give right now. Move one pan to the other side, or switch the zone you need at full power on last, because AEG state that the last-activated zone has priority.

Protection operating. AEG's E4 and Beko's E 22 are overheating protection, and both clear themselves as the hob cools; AEG warn that the H may stay on afterwards, which is the residual heat indicator rather than a second fault. Neff's F8 is a zone that has been on continuously for too long — touch any button and set it again — and if F8 alternates with another symbol, that symbol is residual heat. A zone that cuts out part way through cooking has usually protected itself, and if it only happens with a big pan on a front zone, you have the answer. If any of these happens repeatedly on ordinary cooking, look under the hob rather than at it: a drawer that looks fine when open can be packed tight against the underside when closed, and air has to move through that cavity.

Demo mode. dE means the hob is set up for a showroom floor — it responds to touch and never heats anything. The exit sequence is in your own manual, and BSH publish two different ones across model generations, so the sequence for another hob of the same brand may not be yours. Start from a genuine power-off at the wall switch, follow the sequence exactly including any hold, and if it does not take, begin again from the isolator rather than from where you got to.

The codes that are the wiring

A family of hob codes appears within days of a kitchen being fitted, and none of them is inside the hob. U400 on several brands means the hob has been connected to a supply it will not accept — Neff's wording is that the hob is not connected correctly, Bosch's that the supply voltage is incorrect, and the usual cause is a two-phase 400-volt connection where the hob wanted 230 — and the continuous tone is the hob telling you not to leave it energised. AEG E3 and E311 are the same message, and AEG name the person to ring: the qualified electrician who installed it, not their service line. AEG E6 is the hob only getting one phase when it needs more, with AEG's note that induction hobs usually want a 16 amp supply. AEG E8 divides on one question — has this hob ever worked? A new install means a missing phase in the wiring; a hob that worked and stopped means the electronics. Neff 513 is tied by Neff to before first use, which makes it an installation error, and their remedy is to have whoever connected it come back. Beko E 42 is named as an incorrect wiring connection. Rangemaster EC is a supply voltage error: reset once, and if it recurs, note whether it coincides with a shower or a kettle starting, and call an electrician rather than an appliance engineer.

For all of these: switch the hob off at the cooker switch on the wall, establish when it started, and ring whoever wired it rather than the manufacturer. Have the manual to hand, because the required connection arrangement is printed in the installation section and it is what the electrician needs. Do not open the cooker outlet or the terminal block yourself — this is fixed wiring on a high-current circuit, and a loose terminal there is a fire risk rather than an inconvenience. Under Part P, correcting a connection is a repair and is not notifiable, but a new cooker circuit is, everywhere, and in Wales so is extending an existing kitchen circuit; either way the work has to meet BS 7671 and it is an electrician's, not yours. AEG state that faults arising from incorrect installation may not be covered under warranty, so a manufacturer's engineer sent to a miswired hob can be a chargeable visit while the installer putting their own work right normally is not.

The published resets

There is no plug. A built-in hob is wired to a cooker circuit, so every reset below runs through the cooker switch on the wall or the RCD or breaker in the consumer unit, and the manufacturers say so.

• AEG: disconnect from the supply for at least thirty seconds and reconnect. AEG give this as the remedy for E7 after clearing the space under the hob, for E8 on a hob that has worked before, and for E9 once — if E9 comes straight back it is the board, and there is no second reset that works. The full thirty seconds matters because the boards hold charge and a flick of the switch does not reset them.
• Beko: thirty seconds off at the wall switch or the breaker, published for FF once the panel is clean, dry and clear.
• Neff: their published power cycle is for F3 — isolate at the cooker switch, wait a few seconds, switch back on. For 141, a code they publish no meaning for, that costs nothing to try once, and then their only instruction is to book an engineer.
• Rangemaster: switch the hob off and on once. That is their published remedy for EC, for the saturation reading of EA, and for the whole C1 to C8 range, and they explicitly sanction continued use after a reset on the C codes. If EC comes with the frequency code, their longer sequence is to switch off, wait for H to clear from every zone, then switch back on. On the hardware reading of EA, Rangemaster describe a risk of destroying the switching transistor if it is repeatedly re-energised, so a code that returns is a stop, not a retry.
• On a gas hob with electronic ignition, AEG's F or E6 means a burner could not be lit, and the reset has a three-second window: switch the hob off and on, wait for the code to reappear, then touch pause and Hob2Hood within three seconds, or press and hold the reset button for three seconds, and look for a zero. Clean and dry the burner cap and crown first. Do not keep resetting a hob that will not light, because every ignition attempt releases gas, and if you can smell gas do not touch any switch — leave the property and ring the gas emergency line from outside.

Two attempts is the limit on any hob code. A code that returns after a proper power cycle is describing a board, a fan, a pan or the wiring, and none of those changes with a switch. Hob faults: what you can fix, who to call, and what it costs draws the line between the checks above and the work that needs someone.

Sources

• Hotpoint UK support, residual heat indicator threshold; Lamona hob user manual, residual heat warning; Beko UK support, residual heat after a power cut and normal operating noise.
• AEG UK support: E3/E311, E4, E6, E7, E8, E9, F, L and "display flashing between two numbers" articles; AEG gas hob ignition fault and reset procedure; retrieved August 2026.
• Bosch and Neff UK support and hob instruction manuals: cookware test, F5, F8, F3 power cycle, 513 and 141, demo mode.
• Beko UK support: E 22, E 27/E 47, E 42 and FF articles; Beko induction hob fault table.
• Rangemaster user guides (the U-numbered series) and Rangemaster UK support: E3, EA, EC and C1 to C8.
• Building Regulations Approved Document P (England) and the Welsh Government equivalent, on notifiable electrical work.
• The published meaning of each code here is on its own page, with the source it was taken from.