F40
Kenmore
ATC (Automatic Temperature Control) or Heater Relay Error
Washer-dryer combo shows F40 and will not start or may stop unexpectedly.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed ATC sensor, wiring issue to temperature components, defective main control board relay, shorted heater
How to Fix / Troubleshooting
Safety first: Disconnect power and allow any hot components to cool.
- Check temperature sensors: Inspect and test the NTC sensor(s) on the tub or heater as described for F23/F24.
- Inspect heater circuit: Check the heater for shorts to ground and proper resistance. A shorted heater can trigger control errors.
- Control board inspection: Remove the top panel and inspect the main control board for burnt areas near heater relays. If damage is visible, replace the board.
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Repair Difficulty
Professional Required
5/5
Required Part
Main Control Board (CCU)
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