Range Hood: Fan turns on by itself
Some models of range hoods have a sentry feature that monitors the air temperature above the cooktop. If the temperature gets hot enough to trip the sentry system, the exhaust fan turns on to cool the cooktop area.
If the range hood fan turns on when the cooktop area is at room temperature, a failed temperature sensor, loose wiring or electronic control board failure could be the cause.
The sentry system uses a temperature sensor to monitor air temperature. If the fan turns on when the area above the cooktop is at room temperature, test the temperature sensor by using a multimeter to check its resistance. Refer to the range hood's tech sheet or technical data for a temperature/resistance chart and replace the temperature sensor if its resistance doesn't match the expected resistance shown on the tech sheet. If the temperature sensor's resistance is okay, check the temperature sensor wiring connections and reconnect any loose wires. If wiring connections are okay, you likely need to replace the electronic control board because the control board isn't detecting the temperature sensor's signal correctly.
Replace the range hood temperature sensor
Some range hoods have a sentry system that monitors the air temperature above the cooktop. A temperature sensor mounted in the range hood measures that air temperature. If the sentry feature turns on when the cooktop area is at room temperature, the sensor could be defective. Replace the temperature sensor if it isn't measuring the temperature properly.
Replace the range hood electronic control board
The electronic control board operates the exhaust fan and cooktop lights in the range hood. If the electronic control board is getting power but won't activate the fan or lights, replace it. The electronic control board also operates the sentry system on models equipped with that feature. Replace the electronic control board if it isn't operating the sentry system correctly.
The fan switch activates the fan motor in the range hood. If the fan switch is defective, replace it using the detailed steps in this repair guide.
The electronic control board activates the fan and lights in the range hood. If the electronic control board is defective, replace it using the detailed steps in this repair guide.
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