Freezer
F5
The F5 error code on a Bosch freezer indicates a fault with the evaporator temperature sensor (NTC sensor), meaning the appliance cannot accurately monitor internal temperatures. It’s a moderately serious fault — your freezer may struggle to maintain safe freezing temperatures until it’s resolved.
What does this error mean?
The F5 code tells you the freezer’s evaporator NTC sensor has either failed, lost its connection, or is reading temperatures outside the expected range. The evaporator sensor feeds temperature data to the control board so it can regulate the compressor and cooling cycle. Without accurate readings, the freezer cannot cool efficiently and may trigger a temperature alarm or shut down the cooling cycle entirely to prevent damage.
Est. repair cost
£10–£25 DIY NTC sensor part; £80–£150 professional sensor repair; £150–£280 if control board replacement is needed
🔍 Likely causes
🛠️ Step-by-step fix
Power off and reset: Unplug the freezer from the wall socket, wait 5 minutes, then plug back in. A temporary sensor glitch can sometimes be cleared with a hard reset — check if F5 returns after the appliance runs for 30 minutes.
Check for excessive ice build-up: If the freezer compartment has heavy frost, run a manual defrost by switching the appliance off and leaving the door open (with towels down). Allow it to fully defrost over 12–24 hours, then restart and monitor.
Inspect the sensor wiring: If you’re comfortable doing so, unplug the freezer, remove the interior rear panel (usually held by 2–4 screws), and visually check the wiring connector running to the evaporator sensor for any obvious looseness, corrosion, or damage. Reseat the connector firmly.
Test or replace the NTC sensor: The evaporator NTC sensor is a small, inexpensive part (typically £10–£25 for a Bosch-compatible sensor). You can test it with a multimeter — at 0°C it should read approximately 10,000 ohms. A reading wildly outside this range confirms a failed sensor. Replacing it involves unplugging the old sensor and clipping the new one in place.
Check your model’s part number: Search your Bosch freezer’s model number (found on the interior rating plate) on a UK spares site such as eSpares or 4ourhouse to confirm the correct NTC sensor part before ordering.
If the error persists after sensor replacement: Do not attempt to test or replace the main control board yourself — this requires disassembly of live electrical components and should be handled by a qualified appliance engineer.
📞 When to call a professional
Call a qualified appliance engineer if the F5 error persists after a full defrost and sensor replacement, as the fault likely lies with the main PCB or wiring loom — both of which require professional diagnosis. When booking, tell the engineer ‘F5 error code, suspected evaporator NTC sensor or PCB fault on a Bosch freezer’ so they can bring the right parts. In the UK, expect a call-out and diagnostic fee of £60–£90 before any repair work begins.
⚖️ Repair or replace?
An NTC sensor replacement by a professional typically costs £80–£150 all-in, which is worthwhile on a freezer under 8 years old. If the fault is the control board, repair costs rise to £150–£280, at which point a freezer over 7–8 years old is often not worth repairing — a new mid-range freestanding freezer costs £250–£450. For appliances approaching a decade old with a PCB fault, replacement is usually the better value decision.