E18
Bosch
Defrost Sensor / Thermostat Fault
E18 error; freezer may not defrost correctly and may show irregular temperature behavior.
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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
Defective defrost thermostat clipped to evaporator, Open or shorted defrost sensor wiring, Incorrect thermostat replacement, Control board misreading defrost sensor
How to Fix / Troubleshooting
Safety: Unplug the appliance before accessing the evaporator area.
Steps:
- Access evaporator: Remove drawers and inner rear panel to expose the evaporator coil and defrost components.
- Locate defrost thermostat: Typically a small round or oval device clipped to the evaporator tubing.
- Test thermostat: At freezer temperature (below freezing), the thermostat should show continuity. If it is open, it is faulty.
- Inspect wiring: Check the wires from the thermostat to the main harness for damage or corrosion.
- Replace thermostat: Install a Bosch-compatible defrost thermostat with the correct temperature rating. Clip it firmly to the evaporator tube.
Note: If the thermostat is good but E18 persists, the main control board may be misinterpreting the defrost circuit and may need replacement.
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Repair Difficulty
Medium
3/5
Required Part
Defrost Thermostat
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