The F12 error on your Indesit Dishwasher means the machine has detected a fault with the water temperature sensor (NTC thermistor). This stops the wash cycle because the control board can’t confirm the water is heating correctly. A power reset often clears it, but a faulty sensor will usually need replacing.

Error code F12
Meaning Water temperature sensor (NTC) fault or wiring failure
Severity Medium — dishwasher won’t heat water or complete cycles properly
Time to fix 15–45 minutes
Tools needed Multimeter, screwdriver

What the F12 error means

The F12 code appears when the dishwasher’s control board can’t get a reliable signal from the water temperature sensor. This sensor tells the machine when the water is hot enough for the wash cycle to proceed. If the reading is missing, out of range, or inconsistent, the dishwasher stops and flashes F12 as a safety measure to avoid running a cycle with incorrect water temperature.

This is similar to how other Indesit appliances flag sensor faults, such as the Indesit Washing F02 Error Code: Causes and Fixes, where a failed sensor triggers a protective stop rather than letting the appliance run incorrectly.

Common causes

  • Faulty NTC temperature sensor that has failed or drifted out of calibration
  • Loose or corroded wiring connector at the sensor or control board
  • Limescale or debris build-up affecting the sensor’s contact with water
  • Damaged wiring harness caused by heat, vibration, or rodent damage
  • Control board fault misreading a working sensor
  • Temporary electrical glitch after a power surge or interruption

How to fix the F12 error

  1. Power cycle the dishwasher — Turn it off at the wall, wait two minutes, then switch it back on. This clears many temporary sensor faults, much like resetting after an Indesit Washing F03 Error Code: Causes and Fixes reset would clear a similar glitch.
  2. Check the wiring connections — Unplug the dishwasher, remove the lower kick panel, and inspect the sensor wiring for loose plugs, corrosion, or fraying. Reconnect firmly if needed.
  3. Test the sensor with a multimeter — Disconnect the NTC sensor and measure its resistance. Compare the reading to the manufacturer’s spec chart (resistance should change predictably with water temperature); a reading of zero or infinite resistance means it’s faulty.
  4. Clean the sensor housing — Remove limescale or debris around the sensor probe, especially if you have hard water, as build-up can interfere with accurate readings.
  5. Replace the faulty sensor — If the multimeter test confirms failure, fit a new NTC sensor matched to your model number. This is a straightforward swap on most Indesit models.
  6. Call an engineer if the fault persists — If the sensor tests fine but F12 still appears, the control board itself may need diagnosis and replacement.

FAQ

Can I still use my dishwasher with an F12 error showing?
It’s best not to. The machine may not heat water properly, leading to poor cleaning results and undissolved detergent. Fix the fault before running further cycles.

Will resetting the dishwasher permanently fix F12?
Sometimes, if it was a one-off electrical glitch. But if F12 returns after a reset, it usually points to a genuine sensor or wiring fault that needs physical repair.

Is the temperature sensor expensive to replace?
NTC sensors are generally inexpensive parts, often under £20–£30, and the labour is minimal if you’re comfortable doing it yourself, similar in cost to fixing an Indesit Washing F04 Error Code: Causes and Fixes issue on a washing machine.