Cooker
F03
The F03 error code on a Smeg cooker indicates a fault with the oven temperature sensor (NTC probe), meaning the appliance cannot accurately read or regulate the oven’s internal temperature. It’s a moderately serious fault — the oven will likely stop working until it’s resolved.
What does this error mean?
F03 signals that the oven’s NTC (Negative Temperature Coefficient) temperature sensor has either failed, lost its connection, or is reading a temperature outside the expected range. The control board uses this sensor to regulate heat; without a reliable reading, it shuts the oven down as a safety measure. This is an electrical fault, not a gas fault — making it safe for some basic DIY investigation.
Est. repair cost
£15–£35 DIY sensor replacement; £80–£150 for a professional sensor repair; £150–£300+ if the control board needs replacing
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 – Reset the oven: Switch the cooker off at the wall, wait 5 minutes, then switch it back on. If the F03 clears, monitor closely over the next few uses.
Step 2 – Check the oven cavity visually: With the oven completely cold and unplugged, look inside the oven for the NTC probe — a small metal rod, usually mounted on the back or side wall. Check for visible damage, burning, or loose mountings.
Step 3 – Inspect the sensor connector: Carefully pull the oven away from the wall (unplug first), remove the back panel if accessible, and check that the sensor’s wiring connector is firmly seated with no visible corrosion or scorch marks. Reseat it firmly if loose.
Step 4 – Test the NTC sensor resistance: If you have a multimeter, disconnect the sensor and test its resistance at room temperature. Most Smeg NTC sensors read approximately 10,000 ohms (10kΩ) at 25°C. A reading of zero or infinity indicates a failed sensor.
Step 5 – Replace the NTC sensor: Smeg NTC sensors are widely available from UK appliance parts suppliers (e.g. 4ourhouse, eSpares) for £15–£35. Replacement involves unscrewing the old probe, disconnecting the wiring, and fitting the new one — suitable for a competent DIYer.
Step 6 – If the sensor tests fine: Stop DIY here. A functioning sensor with a persistent F03 code points to a faulty control board — this requires professional diagnosis and replacement.
📞 When to call a professional
Call an engineer if replacing the NTC sensor does not clear the F03 code, or if you find burnt wiring or damage to the control board. Tell the engineer: ‘My Smeg oven is showing an F03 error — I suspect either the NTC temperature sensor or the control board.’ Avoid opening or probing the main control board yourself, as capacitors can hold charge even when unplugged.
⚖️ Repair or replace?
A Smeg NTC sensor replacement by an engineer typically costs £80–£150 all-in; a control board replacement is significantly more at £150–£300+, depending on the model. If your Smeg cooker is over 10 years old and needs a control board, replacement is often the more economical choice given the cost of parts and labour. Smeg cookers under 8 years old are generally worth repairing — they are a premium brand with good longevity.