Fridge
F3
The F3 error code on a Siemens fridge indicates a fault with the fridge compartment temperature sensor (NTC sensor), meaning the appliance can no longer accurately monitor or regulate its internal temperature. It’s a moderately serious fault — your fridge may stop cooling correctly, putting food at risk.
What does this error mean?
The F3 code tells you the fridge’s NTC (Negative Temperature Coefficient) thermistor — a small sensor that reads the internal temperature — has either failed, is reading outside its expected range, or has lost its connection to the control board. Siemens fridges use this sensor to continuously adjust the compressor and fan to maintain your set temperature. Without a working sensor, the fridge cannot regulate cooling properly and may run constantly, not at all, or display an incorrect temperature.
Est. repair cost
£10–£25 DIY sensor replacement; £80–£180 professional repair (sensor or control board, parts and labour included)
🔍 Likely causes
🛠️ Step-by-step fix
Reset the fridge: unplug it from the wall, wait 5 minutes, then plug back in. If F3 clears and does not return within 24 hours, a power glitch was the likely cause.
Check for ice build-up: open the fridge and inspect the rear wall and any visible sensor probe for a thick frost layer. If iced over, defrost the fridge fully by leaving it unplugged with the doors open for 6–8 hours, then restart.
Locate the NTC sensor: it is typically a small plastic probe clipped to the rear interior wall or mounted near the evaporator. Check the wire running from it — look for obvious damage, kinks, or a connector that has simply come loose. Firmly reseat any loose connector.
Test the sensor resistance (if you own a multimeter): disconnect the sensor connector and measure resistance across the sensor terminals. At room temperature (~20°C) a healthy NTC sensor should read approximately 5,000–10,000 ohms. A reading of zero or infinite resistance confirms a failed sensor.
Replace the NTC sensor: compatible sensors for Siemens fridges are available from UK parts suppliers (e.g. eSpares, 4ourhouse) for £10–£25. Note your fridge model number (inside the door frame) before ordering. Unplug the fridge, unclip the old sensor, plug in the new one, and restart.
If the error returns after replacing the sensor, stop DIY work — the fault likely lies with the control board, which requires a professional.
📞 When to call a professional
Call a qualified appliance engineer if the F3 code returns after a reset, a full defrost, and a new NTC sensor has been fitted — this points to a faulty control board, which involves working inside the appliance’s electronics and is not a safe DIY job. When booking, tell the engineer: ‘Siemens fridge showing F3 error, NTC sensor already replaced, suspected control board fault.’ This will save diagnostic time and cost.
⚖️ Repair or replace?
A professional repair for an NTC sensor or control board on a Siemens fridge typically costs £80–£180 in the UK, including parts and labour. If your fridge is under 8 years old and the fault is sensor-only, repair is almost always worthwhile — Siemens is a premium brand built to last 12–15 years. If the fridge is over 10 years old and a control board replacement is needed (£120–£180+), weigh that cost against a new mid-range fridge at £350–£600 and consider replacement.