Freezer
F3
The F3 error code on a Bosch freezer indicates a fault with the temperature sensor (NTC sensor) inside the freezer compartment. It’s a moderately serious fault — your freezer may struggle to maintain safe temperatures, putting your food at risk.
What does this error mean?
F3 tells you that the freezer’s internal temperature sensor is sending a reading that is out of range — either a short circuit or an open circuit in the sensor itself. The control board can no longer reliably measure the compartment temperature, so it raises the alarm. In most Bosch freestanding and integrated freezers, this is specifically the evaporator or cabinet NTC thermistor.
Est. repair cost
£80–£150 professional repair; £10–£25 DIY NTC sensor replacement part
🔍 Likely causes
🛠️ Step-by-step fix
Reset the freezer first: unplug it from the wall, wait 5 minutes, then plug it back in. If the F3 code clears and doesn’t return, a temporary glitch caused it — monitor for recurrence.
Defrost the freezer manually: if there is significant ice build-up around the back wall or base, switch off the appliance, remove all food to a cool bag, and allow it to defrost fully for 24 hours. Ice covering the sensor can trigger false F3 readings.
Check the door seal: run your finger around the rubber gasket. If it’s torn, stiff, or pulling away, cold air is escaping and causing temperature instability. Replacement seals cost £15–£30 and clip or glue into place without tools.
Locate and inspect the NTC sensor: it is usually clipped to the evaporator or mounted on the rear inner wall. With the freezer unplugged, check the sensor’s wiring connector — unplug it and reconnect it firmly. Look for visible damage, corrosion, or broken wires.
Test or replace the NTC sensor: a working NTC thermistor typically reads around 5,000–10,000 ohms at room temperature using a multimeter set to resistance (Ω). If it reads open circuit (OL) or zero, it has failed. Bosch-compatible NTC sensors cost £10–£25 online — search using your full model number (found inside the door frame).
If the sensor tests fine but the F3 code persists after a reset, the control board is the likely culprit — this requires a professional repair. Do not attempt to open or repair the control board yourself.
📞 When to call a professional
Call a qualified appliance engineer if the F3 code returns after a manual defrost and sensor replacement, or if you are not comfortable testing components with a multimeter. When you call, tell the engineer: ‘My Bosch freezer is showing an F3 error, which I understand is a temperature sensor fault — I’d like them to check the NTC sensor and wiring harness.’ This saves diagnostic time and cost.
⚖️ Repair or replace?
A professional repair for an F3 fault — covering diagnosis, NTC sensor replacement, and labour — typically costs £80–£150 in the UK. If your Bosch freezer is under 8 years old, repair is almost always worth it; Bosch appliances are built to last 10–15 years. If the appliance is over 10 years old and the control board is also faulty, replacement with a new Bosch or equivalent freezer (£250–£600) is the more cost-effective long-term choice.