Bosch error code E305: The hot-surface indicator sensor (which lights up when the cooktop is hot) is reading out of specification. The cooktop continues to function but the safety indicator may not work correctly.
The hot-surface indicator sensor (which lights up when the cooktop is hot) is reading out of specification. The cooktop continues to function but the safety indicator may not work correctly.
Disconnect power. Locate the thermistor (usually near the heater or on the wash tub). Check the connector for loose pins or corrosion. Reconnect firmly.
Tools needed: Screwdriver set
With power off, disconnect the thermistor connector. Measure its resistance with a multimeter. At room temperature (20°C / 68°F) most NTC thermistors read around 10,000–15,000 Ω. Refer to your model's service sheet for exact values. A reading of 0 Ω (short) or infinite Ω (open) means replace the sensor.
Tools needed: Multimeter
A shorted heater element can pull down the thermistor reading. Disconnect the heater terminals and retest the thermistor in isolation. If the thermistor reads correctly with the heater disconnected, test the heater separately.
Tools needed: Multimeter
Moisture in the sensor connector can mimic a shorted thermistor. Dry the connector with a hair dryer on low heat and reconnect. Run a cycle to see if the error clears.
Tools needed: Hair dryer
If the sensor tests out of specification, replace it with the OEM part for your model. Thermistors are typically inexpensive ($10–$30) and require only a screwdriver to replace.
Tools needed: Screwdriver set