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Ariston F03 on a washer dryer

The water temperature sensor has failed or its circuit is broken.

The same code appears on Hotpoint, Indesit and Whirlpool machines — they share the same control platform.

Verdict

Needs an engineer

Mains electrical, gas or sealed-system work

Urgency
Fix soon

About 55 min to work through

Typical cost

£85–£180

What F03 actually means

The NTC sensor that reports wash temperature has gone out of range, so the board can no longer control heating safely and stops. Often the machine will still run cold programmes. It is a small, inexpensive part, but it sits behind the drum next to the element, so getting to it is the bulk of the job.

Before you start

  • Electrical safety: The sensor sits alongside the mains heating element. Do not attempt access without isolating the machine and the competence to work near mains wiring.

What causes it, most likely first

  1. Failed NTC thermistor

    Most likely

    The sensor drifts out of range or goes open circuit with age and thermal cycling. The part itself is cheap.

    NTC temperature sensor£8–£22 for the partEngineer

  2. Corroded sensor connections

    Common

    Damp behind the drum corrodes the spade terminals until the resistance reads as an out-of-range sensor.

    Wiring loom / connector£10–£45 for the partEngineer

  3. Chafed wiring to the sensor

    Occasional

    Vibration wears through insulation where the loom passes the tub, producing an intermittent fault that comes and goes with drum movement.

    Wiring loom / connector£10–£45 for the partEngineer

  4. Control board fault

    Rare

    The board input reading the sensor fails. Diagnosed only after the sensor and its wiring test good.

    Main control board (PCB)£70–£220 for the partEngineer

How to fix it, step by step

  1. Power-cycle to rule out a latch

    Switch off at the wall for five minutes and restore power before anything else.

    10 min

  2. Test a cold programme

    Run a cold or 20°C wash. If it completes normally, you can keep using the machine on cold cycles until an engineer can attend.

    40 min

  3. Book the repair and quote the code

    F03 tells the engineer to bring an NTC sensor. It is a cheap part and a moderate labour job — expect the labour to dominate the bill.

    5 min

Need an engineer for this F03?

We list 4 washer dryer repair businesses across the UK. Diagnostic callouts typically start around £55, and many will put that towards the repair if you go ahead.

Find washer dryer engineers near you

Parts you might need

Typical UK prices for the part alone, before fitting. Worth knowing before you accept a quote — the part is often a small share of what a repair is priced at.

  • NTC temperature sensor

    A small thermistor that tells the control board how hot the water is. When it fails the board usually assumes the worst and stops heating.

    £8–£22

  • Wiring loom / connector

    Chafed wires and corroded connectors mimic dead components. An engineer will always check continuity before condemning a part.

    £10–£45

  • Main control board (PCB)

    The appliance brain. Genuine boards are expensive and often need configuring to the model, so this is rarely a DIY part.

    £70–£220

Worth repairing, or replace it?

At the top of this range the repair costs a significant share of a graded replacement, which typically starts around £280. Worth getting the quote first, then deciding — on a machine under about five years old a repair usually still wins.

Work out if it's worth fixingCompare graded washer dryers

Related problems

Other Ariston washer dryers codes

All Ariston washer dryers fault codes