Fridge
F4
The F4 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 food may be at risk if left unaddressed.
What does this error mean?
The F4 code tells you that the fridge section’s NTC (negative temperature coefficient) thermistor has either failed, lost its connection, or is sending readings outside the expected range. The fridge’s control board relies on this sensor to maintain the correct temperature, typically between 2°C and 8°C. Without a reliable signal, the fridge may overcool, undercool, or shut down cooling entirely to protect itself.
Est. repair cost
£10–£30 DIY sensor replacement; £80–£160 professional repair including parts and labour
🔍 Likely causes
🛠️ Step-by-step fix
Reset the fridge: Unplug it from the mains, wait 10 minutes, then plug it back in. If the F4 code clears and doesn’t return within 24 hours, a temporary glitch was the cause.
Check for excessive ice build-up: Open the fridge compartment and inspect the back panel. If heavily iced over, perform a manual defrost by unplugging the fridge and leaving the doors open for 24–48 hours with towels on the floor to catch water. Re-plug and check if the code returns.
Locate the NTC sensor: It is usually clipped to the back wall of the fridge interior or mounted near the evaporator behind the rear panel. Consult your model’s manual or the Siemens website for the exact location.
Inspect the sensor and wiring: Without opening sealed electrical components, check that the sensor connector is firmly seated and the wiring shows no obvious cuts, kinks, or corrosion. Reseat any loose connectors by hand.
Test or replace the NTC sensor: NTC sensors for Siemens fridges are inexpensive (£10–£30) and widely available on sites like eSpares or BuySpares. Match the part number to your model. Replacing the sensor involves unplugging the old one and clipping in the new one — no specialist tools required.
If the code persists after a new sensor, do not attempt to repair the main control board yourself. Stop here and call a qualified appliance engineer.
📞 When to call a professional
If the F4 code returns after a reset, a manual defrost, and a sensor replacement, the fault is likely in the main control board or the wiring loom — both of which require a qualified appliance engineer. When calling, tell them: ‘My Siemens fridge is showing an F4 error code, which I understand relates to the fridge compartment NTC temperature sensor, and I’ve already replaced the sensor.’ This saves diagnostic time and cost.
⚖️ Repair or replace?
A professional repair for an F4 fault typically costs £80–£160 depending on whether it’s a sensor replacement or a control board fault. If your Siemens fridge is under 8 years old and was a mid-to-high-end model (original price £600+), repair is almost always worthwhile. If it’s over 10 years old or a budget model, a replacement fridge may offer better long-term value — budget £400–£900 for a comparable Siemens or equivalent.