The Maytag F18 error code on a washer typically indicates a problem with the machine’s temperature sensing or heating circuit — most commonly a fault with the water temperature sensor (NTC thermistor) or its related wiring and controls. When the washer can’t read or regulate water temperature correctly, the control board may halt or modify cycles to protect the appliance and your laundry. You may notice incomplete cycles, unusually long wash times, incorrect temperature selection (water not getting hot or staying cold), or the washer stopping with an error displayed. In some cases, poor temperature regulation can lead to less effective cleaning, residue build-up on fabrics, and (rarely) a potential risk if a shorted circuit creates excessive heat. Identifying the exact cause early helps avoid repeated cycle interruptions and potential damage to the main control board or heater assembly.
Common causes
- Failed or out-of-spec temperature sensor (NTC thermistor).
- Broken, corroded or disconnected wiring/connectors between the sensor and control board.
- Faulty main control board or electronic control module.
- Defective heating element (if model uses a heater) or related relay not switching.
- Blown thermal fuse or safety thermostat interrupting the circuit.
- Moisture intrusion in the console or control area causing intermittent faults.
- Software/firmware glitch that may be resolved by a power reset.
Troubleshooting steps
- Safety first: Unplug the washer or switch off its circuit breaker before inspecting components. Water and electricity are hazardous.
- Power-cycle the washer: Leave it unplugged for 1–5 minutes and restore power. Sometimes the code clears if it was a transient error.
- Run diagnostics: If your model supports a service/diagnostic mode, run the built-in test to confirm the F18 and any additional codes that narrow the cause.
- Inspect visible wiring and connectors: Check harnesses around the front panel, control board, and temperature sensor for damage, corrosion, or loose connectors.
- Test the temperature sensor: Locate the NTC thermistor and use a multimeter to check its resistance at room temperature (compare with the tech sheet/service manual). An open circuit or wildly out-of-spec reading indicates a failed sensor.
- Check heating element & thermal fuses: If your model heats water, verify the heater element and safety thermostats for continuity. A failed heater or blown thermal fuse can trigger temperature-related errors.
- Swap or bypass carefully: If you have a known-good sensor or connector, briefly swap to confirm the fault — only if you are experienced and the appliance is de-energized.
- Inspect cont