- Turn the hob off at the circuit breaker or isolator for at least 60 seconds.
- Restore power and check whether the display clears before selecting any zone.
- If the code returns immediately, stop using the hob and continue with the checks below.
Overheating protection is operating (possible installation issue or unsuitable cookware). On AEG hobs this usually points to the hob overheating protection operating because of heat buildup, unsuitable cookware, or installation airflow problems, and persistent faults often need service or installation checks.
- E421 remains on the display instead of normal zone information.
- One or more cooking zones may not heat or controls may behave abnormally.
- The hob may appear to recover after a reset and then show the code again.
- The hob overheating protection operating because of heat buildup, unsuitable cookware, or installation airflow problems.
- Temporary control-board glitch after a power event.
- Electrical supply, connection, or internal module problem.
- Check whether the fault started after a new installation, outage, or recent electrical work.
- Confirm the hob surface is dry, clean, and free from spills around the controls.
- After power is restored, test one cooking zone at a time and note when the code reappears.
- Record the model, code, and any recent changes to the appliance or supply before contacting support.
| Checkpoint | What to check | Good result | If it fails |
|---|---|---|---|
| Power reset | Hob isolated for 60 seconds and restarted | Code clears and stays away | Escalate if it returns |
| Control area | Surface is dry and controls respond normally | Normal operation resumes | Stop using if controls stay erratic |
| Electrical context | No recent supply or install issues | Hob starts normally | Ask an electrician or service engineer to inspect |
- Continuing to cook while the same code remains active.
- Ignoring installation or power-supply issues after recent fitting work.
- Attempting internal electrical repairs without training.
- Do not dismantle internal panels or touch live electrical parts.
- Do not keep resetting the hob repeatedly if the fault comes back immediately.
- Always isolate mains power before any inspection or cleaning around the hob.
- If you smell burning, see smoke, or the hob trips the supply, stop immediately and call for service.
Book service if E421 returns after a proper power reset, or immediately if the hob was recently installed and the code points to supply or connection problems.
- Keep the control area dry and free from residue after cooking or cleaning.
- Use a qualified installer or electrician for any wiring or supply changes.
- Do not ignore intermittent electrical faults that appear before full failure.
Can E421 clear on its own?
Sometimes a full power reset clears a temporary glitch, but a persistent return usually means the underlying issue is still there.
Should I keep using the hob if it works after a reset?
Only if the code stays away. If it returns, stop using the hob until the cause is identified.