Fridge
F1
The F1 error code on a Siemens fridge is your appliance’s way of telling you it has detected a temperature sensor fault — most commonly a problem with the internal NTC (negative temperature coefficient) sensor that monitors the fridge compartment temperature. While it sounds alarming, this fault ranges from a straightforward reset to a sensor replacement that most confident DIYers can handle safely. In this guide, you’ll learn exactly what triggers the F1 code, the most likely culprits, step-by-step fixes to try at home, and when it’s time to call in a professional.
What does this error mean?
On Siemens fridge-freezers and freestanding fridges — including popular models in the iQ300, iQ500, and iQ700 ranges — the F1 error code signals a fault with the fridge compartment temperature sensor, also known as the NTC thermistor. This small electronic component continuously measures the air temperature inside the fridge and sends that data to the main control board. When the board receives a reading that is outside the expected range (either an open circuit, a short circuit, or a wildly implausible temperature value), it throws the F1 code and may activate an audible alarm. In practical terms, this means your fridge may no longer be cooling correctly, or it may be overcooling — both of which can spoil your food if left unresolved. The appliance is not necessarily broken beyond repair; it is simply telling you that communication with the temperature sensor has broken down.
Est. repair cost
DIY sensor replacement: £8–£25 for the part. Professional repair (sensor or wiring): £80–£150. Professional repair (control board): £150–£250 including parts and labour.
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Perform a hard reset: Switch the fridge off at the wall socket, wait a full 5 minutes, then switch it back on. This clears any temporary software glitch or post-power-cut error. Many F1 codes caused by voltage spikes disappear after a proper reset — no tools needed.
Step 2 — Check for an audible alarm and silence it: If your model has a temperature alarm button (usually labelled with a bell icon on the control panel), press and hold it for 3 seconds to silence the beep while you investigate. Refer to your model’s manual — available free on Siemens’ UK website using your model number (found inside the door frame).
Step 3 — Inspect the fridge interior for frost build-up: Open the fridge and look for excessive ice or frost around the back wall or top of the compartment. If you find it, remove all food, place towels on the shelves, and leave the fridge door open (switched off) for 24–48 hours to fully defrost. Frost encasing the sensor is a surprisingly common and fully fixable cause of F1.
Step 4 — Check the door seal: Run your finger around the full perimeter of the fridge door seal (gasket). Feel for cracks, tears, or sections that no longer grip the cabinet firmly. A simple test: close the door on a piece of A4 paper — if you can pull it out easily, the seal is failing. Replacement Siemens door seals cost £15–£35 online and clip or screw into place without any electrical work.
Step 5 — Locate and visually inspect the NTC temperature sensor: On most Siemens fridge models, the NTC sensor is a small cylindrical or oval component (roughly 1–2cm long) clipped to the back wall inside the fridge compartment, often near the top. It will have a thin two-wire harness running from it. You do NOT need to open the back panel of the appliance to access it — it is inside the fridge cavity. Check that the connector is firmly seated and that the wires are not visibly damaged or pinched.
Step 6 — Test the sensor with a multimeter (confident DIYers only): If you own a multimeter, disconnect the sensor’s two-pin connector (no mains electricity is involved once you unplug the fridge). Set the multimeter to resistance (Ohms). At room temperature (around 20°C), a healthy Siemens NTC fridge sensor should read approximately 5,000–6,000 Ohms (5–6kΩ). A reading of zero (short circuit) or OL/infinite (open circuit) confirms the sensor has failed and needs replacing.
Step 7 — Replace the NTC temperature sensor: Replacement NTC sensors compatible with Siemens iQ-series fridges are widely available from UK suppliers such as 4ourhouse, eSpares, or ApplianceSparesParts.co.uk for £8–£25. Ensure you order using your full model number. With the fridge unplugged, simply unclip the old sensor from its mount, disconnect the two-pin connector, connect the new sensor, clip it into place, and restore power. No soldering or specialist tools are required.
Step 8 — Clean the condenser coils at the rear: With the fridge unplugged and pulled away from the wall, use a vacuum cleaner with a brush attachment to gently remove dust and debris from the condenser grille at the back. This takes around 10 minutes and should be done annually. Restore power afterwards and monitor whether the F1 code returns.
Step 9 — Monitor after any fix: After completing any of the above steps, restore power and watch the display for at least 30 minutes. The fridge should return to its set temperature (typically 4°C) and the F1 code should clear. If the code returns within a short period, the fault lies deeper — likely the control board — and you should stop and call a professional.
Step 10 — Do NOT attempt to open the appliance’s rear panel or touch the main control board: Accessing the PCB or refrigerant system requires specialist knowledge and equipment. If steps 1–9 have not resolved the F1 code, this is where DIY ends — call a qualified appliance engineer.
📞 When to call a professional
You should call a qualified appliance repair engineer if: the F1 code returns immediately after a hard reset and you can find no obvious cause such as frost or a loose connector; the sensor tests correctly on a multimeter but the error persists (pointing to a control board fault); or you are not comfortable working with the internal components of the appliance even with it unplugged. When you call, tell the engineer: ‘My Siemens fridge is showing an F1 error code, which I understand relates to the temperature sensor. I have already performed a hard reset [and/or replaced the NTC sensor if applicable], but the fault persists.’ This saves diagnostic time and may reduce your call-out fee. Look for engineers registered with Which? Trusted Traders or those who specifically list Siemens appliance repair experience. Siemens’ own UK service line (0344 892 8999) can also book an authorised engineer, though this is typically more expensive than an independent repairer.
⚖️ Repair or replace?
For most UK households, repair is the right call — provided the fridge is under 8 years old and the fault is sensor or wiring related. A new Siemens NTC sensor is £8–£25 as a DIY fix, or £80–£150 all-in with a professional call-out. If the control board has failed, professional repair typically costs £150–£250 including parts and labour — at this point, weigh it against the cost of a comparable replacement fridge. A mid-range Siemens iQ300 fridge-freezer retails for £500–£900 new in the UK. As a rule of thumb: if the repair cost exceeds 50% of the replacement cost and the appliance is over 8–10 years old, replacement is the more economical choice. Siemens spare parts are generally well-stocked in the UK — far better than some smaller brands — so parts availability is rarely a barrier to repair on models up to 12 years old.