F4
JennAir
Zone Defrost Sensor or Heater Fault
Wine cooler displays F4 and may not defrost properly in one zone, leading to frost buildup.
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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 zone defrost thermistor, Open defrost heater for that zone, Wiring issue in zone defrost circuit, Faulty control board defrost output
How to Fix / Troubleshooting
Safety: Unplug the wine cooler before accessing the evaporator or heater.
Steps:
- Inspect frost pattern: Remove interior panel for the affected zone and check for heavy ice on the evaporator.
- Test defrost thermistor: Disconnect and measure resistance; replace if open/shorted or out of spec.
- Check heater continuity: Disconnect heater leads and test with a multimeter. Replace the heater if open.
- Inspect wiring: Repair any burnt or broken wires between heater, sensor, and control board.
- Control board: If components test good but F4 persists and defrost never occurs, the control board may be faulty.
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Repair Difficulty
Hard
4/5
Required Part
Zone Defrost Heater
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