Chimney-style range hood with a glass canopy over a cooktop

Generic photo: Bilguun Gantumur · Pexels License

Range hood turns on by itself or jumps to high speed

Many hoods (e.g. Broan Heat Sentry and similar) have a heat sensor that starts the fan or raises speed when it senses excess heat. That is a safety feature, not a fault. If it runs with a cold cooktop, suspect the sensor, a stuck switch or the control.

Cross-checked ~20 min easyBrands: All

Before you start

Turn off the breaker before opening the hood or touching wiring
Use a non-contact tester to confirm power is off
Capacitor terminals can shock: discharge or handle by insulated tools

Diagnostic steps

Unlock all 3 steps with expected values

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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