E04
Bosch Refrigerator
Severity: ModerateWhat Does This Error Mean?
E04 on a Bosch refrigerator indicates a fault with the defrost sensor (also called the evaporator temperature sensor). This sensor monitors the temperature of the evaporator coil during the defrost cycle. Without it, the control board cannot tell when the coil has been fully defrosted.
Affected Models
- Bosch Series 4 Refrigerator
- Bosch Series 6 Refrigerator
- Bosch Series 8 Refrigerator
- Bosch Benchmark Series Refrigerator
Common Causes
- Defrost sensor (evaporator NTC thermistor) has failed — resistance out of range
- Sensor connector loose or corroded on the control board
- Sensor wire damaged by ice formation or physical contact with the coil
- Control board fault causing incorrect sensor reading
How to Fix It
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Unplug the refrigerator for 10 minutes, then restore power.
A temporary sensor reading error can sometimes clear with a power reset. If E04 returns, the sensor itself has likely failed.
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Call a technician to test the defrost sensor resistance.
The sensor resistance at 0 degrees C should be approximately 10k ohms. A reading of 0 or infinite resistance confirms a faulty sensor. Replacement sensors are low-cost parts.
When to Call a Professional
E04 requires a technician to access the evaporator coil area behind the freezer back panel. Sensor testing and replacement involves the freezer interior panels — professional diagnosis is recommended.
Frequently Asked Questions
Is E04 the same as E03 on a Bosch refrigerator?
No. E03 means the defrost cycle failed to complete — a system-level fault. E04 means the defrost sensor itself is reporting an error — a component-level fault. E04 will often lead to E03 appearing soon after, since the control board cannot monitor the defrost cycle properly.
Can I keep using the fridge with E04 showing?
Short-term yes, but without a working defrost sensor, the control board may run the defrost heater too long (risking food damage from warmth) or not long enough (causing ice buildup). Get it repaired within a week or two.