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.

range hood

These repairs may help solve your range hood problem

Replace the range hood temperature sensor

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

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.

How to replace a range hood electronic control board

If your range hood's fan or lights don't work, the electronic control board could be the problem. This step-by-step repair guide shows how to replace a range hood electronic control board.

Repair difficulty
Time required
 45 minutes or less
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Symptoms common to all range hoods

Choose a symptom to see related range hood repairs.

Main causes: clogged air filters, air duct problems, fan motor failure, broken fan blade
Main causes: sentry feature trips due to high cooktop temperature, bad temperature sensor, electronic control board failure
Main causes: electronic control board failure, bad user interface control, light and fan switch failures, wiring failure
Main causes: bad fan switch, electronic control board failure, faulty user interface control, wiring failure
Main causes: lack of electrical power, bad electronic control board, faulty user interface, fan and light switch failure, wiring problems
Main causes: loose mounting screws, bad fan motor, damaged fan blade, worn fan motor bearings
Main causes: bad light bulb, broken light switch, bad electronic control, user interface control failure, bad light socket, wiring failure

Repair guides common to all range hoods

These step-by-step repair guides will help you safely fix what’s broken on your range hood.

December 1, 2013
By Lyle Weischwill
How to replace a range hood fan switch

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.

Repair difficulty
Time required
 30 minutes or less
How to replace a range hood electronic control board

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.

Repair difficulty
Time required
 45 minutes or less
January 20, 2013
By Lyle Weischwill
How to replace a range hood light socket

When you replace a light bulb and it still won’t work, the socket is likely defective. Use the detailed steps in this repair guide that show you how to replace it.

Repair difficulty
Time required
 15 minutes or less

Articles and videos common to all range hoods

Use the advice and tips in these articles and videos to get the most out of your range hood.

December 2, 2015

Wiring schematic symbols explained video

By Sears PartsDirect staff

Learn some of the most common symbols found in a wiring diagram and what they mean.

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How to clean stainless steel appliances video

By Sears PartsDirect staff

Learn how to keep the stainless-steel appliances in your home clean and shining bright.

November 1, 2014

Range hood common questions

By Sears PartsDirect staff

See what questions many people have about using, maintaining and and repairing their range hoods.