What this error means
Temperature sensor fault — the NTC thermistor is giving an incorrect or absent reading
The F03 error means the NTC temperature sensor has returned a value outside the expected operating range — either too high, too low, or open circuit. This prevents the machine from managing wash temperature correctly. F03 is a sensor fault specifically — if the heating element itself has failed the machine displays F08. A wiring fault to the sensor can also produce F03.
What you'll need first
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Step-by-step
Symptoms to look for
- F03 displayed partway through a wash programme
- Laundry coming out at the wrong temperature — too cold or occasionally too hot
- Machine takes significantly longer than the displayed time to complete a hot programme
- F03 appears consistently on hot programmes but not on cold washes
Diagnostic steps
Unplug the machine and hold the power button for 10 seconds. Leave unplugged for 5 minutes. Plug back in and run a 40-degree programme. Monitor whether F03 reappears.
With the machine completely unplugged, remove the rear panel. The NTC thermistor is a small cylindrical or oval sensor mounted on or very near the heating element at the lower rear of the drum casing. It connects to the main harness by two thin wires and a small plug connector.
Disconnect the sensor's two-pin connector from the harness. Set a multimeter to resistance. Touch one probe to each terminal. At room temperature (approximately 20 degrees Celsius) a healthy Indesit NTC thermistor reads between 10,000 and 50,000 ohms. A reading of zero indicates a short circuit. OL (open circuit) means the sensor has failed completely.
With the sensor disconnected and the multimeter connected, gently flex the sensor body and its two leads while watching the resistance reading. If the value fluctuates, drops to zero momentarily, or goes to OL and recovers, there is a hairline break inside the sensor body. Replace the sensor even if it reads correctly when stationary.
Trace the two thin wires from the sensor to the harness connector. Look for chafed insulation where the wires pass near the drum, any section pinched against a metal edge, and the condition of the connector pins. Disconnect and firmly reconnect the harness connector.
Indesit NTC thermistors are low-cost and widely available. If the resistance test is outside range or intermittent, replace the sensor and run a 60-degree test cycle.
When to call an engineer
- NTC thermistor reads open circuit or zero — sensor has failed and must be replaced
- Resistance fluctuates when the sensor is flexed — internal wire break, replace the sensor
- Sensor wiring connector is corroded and cannot be cleaned — loom section needs replacing
- Sensor reads within range but F03 persists on every cycle — control board input circuit fault
Frequently asked questions
What is the NTC sensor and why does it cause F03?
What is the difference between F03 and F08 on an Indesit washing machine?
Can F03 appear even if the machine is heating correctly?
Is F03 always the sensor or could it be the wiring?
🎯 What is likely causing this fault?
⚠️ Estimates based on common faults — not a guaranteed diagnosis. Always verify before ordering parts.
Parts you may need
Enter your model number to filter results to your exact machine
Usually found on a label inside the door frame or on the back panel of the machine.
| Part | Approx. UK Cost | Find it |
|---|---|---|
| NTC Thermistor | £10 - £15 | 🛒 Amazon UK → |
| NTC Thermistor | £5 - £15 | 🏷️ eBay UK → |
ℹ️ Prices are approximate. Always check the part number matches your model before ordering. Not sure of your model number? Find out how to locate it here.