Oven
F23
The F23 error code on a Siemens oven indicates a fault with the oven’s temperature sensor or a cooling fan issue — it’s a moderate fault that will prevent the oven from heating safely until resolved.
What does this error mean?
F23 signals that the oven’s control system has detected an abnormal temperature reading, typically pointing to a faulty NTC (negative temperature coefficient) temperature sensor or a problem with the cooling fan circuit. The oven cannot accurately monitor its internal temperature, so it locks out heating as a safety precaution. In some Siemens models, F23 specifically flags that the cooling fan has stopped responding or is running outside its expected parameters.
Est. repair cost
£80–£150 professional repair; £15–£35 DIY NTC sensor replacement (part only)
🔍 Likely causes
🛠️ Step-by-step fix
Hard reset first: switch the oven off at the wall socket (or trip the circuit breaker), wait 5–10 minutes, then restore power. If F23 clears and doesn’t return within a heating cycle, the fault may have been a temporary glitch.
Check the oven’s ventilation: ensure there is adequate clearance around a built-in oven as per the installation manual. Clear any dust or debris from the vents at the rear or top of the appliance.
Listen for the cooling fan: when the oven is switched on, you should hear the cooling fan running. If it’s silent or unusually loud, the fan motor or capacitor is likely the fault — stop here and call a technician.
Inspect the temperature sensor connection (if confident doing so safely with power OFF at the mains): the NTC sensor is usually located on the rear interior wall of the oven cavity. Check that its wiring plug is firmly seated and free from visible corrosion. Do not open any sealed electrical enclosures.
Replace the NTC temperature sensor if you’ve confirmed it’s faulty using a multimeter (resistance at room temperature should be approximately 1,000–1,100 ohms for a standard NTC sensor). Genuine Siemens replacement sensors cost £15–£35 and are clip- or screw-fitted — a manageable DIY task with the oven fully isolated from the mains.
If the sensor checks out and the fan appears functional but F23 persists, the PCB is the likely culprit — do not attempt to repair or replace the PCB yourself; book a qualified appliance engineer.
📞 When to call a professional
Call an appliance engineer if the cooling fan is not running, if a new sensor doesn’t clear the fault, or if you’re not comfortable working near internal oven components. When booking, tell the engineer: ‘My Siemens oven is showing error code F23 — I suspect a temperature sensor or cooling fan fault.’ This helps them arrive with the right parts.
⚖️ Repair or replace?
A professional repair for F23 — covering diagnosis, sensor replacement or fan motor swap — typically costs £80–£150 in the UK including labour. If your oven is under 8 years old, repair is almost always worth it. For ovens 10 years or older where the PCB is also suspect, replacement becomes more cost-effective given that a new mid-range Siemens built-in oven starts at around £400–£600.