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Quick answer
If a range hood cycle does not complete, determine whether Heat Sentry is responding to cooking heat or the fan is stuck after cooling. Broan-NuTone says Heat Sentry can run the blower high until temperature drops, then turn off or return to the last setting. A cool hood that ignores controls, smells hot, or makes abnormal noise needs service.

Work through in order
Diagnostic checks
Use only checks that match the exact appliance or system and its official guide.
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Check 1
Stop cooking and observe whether the fan is high while the area is still hot.
Expected result: Fan slows/stops as area cools or remains high after cooling.
Next step: Allow cooling and monitor once; isolate power safely and arrange service if it remains on.
Stop if: Stop if there is a safety hazard or internal access would be required.
Why this matters
Why: The first pattern can be normal Heat Sentry; persistence suggests sensor/control/motor trouble.
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Check 2
Check for selected delay/timer and whether the documented off/cancel control changes the fan.
Expected result: Delay clears or controls do not respond.
Next step: Use exact manual for timer cancellation; service if controls fail.
Stop if: Stop if there is a safety hazard or internal access would be required.
Why this matters
Why: A timer can explain a finite cycle; unresponsive controls indicate control/electrical fault.
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Check 3
After power is off and hood is cool, inspect grease filters/intake for heavy buildup.
Expected result: Filters loaded or clear but cycle continues.
Next step: Clean as manual allows; do not add an external fan.
Stop if: Stop if there is a safety hazard or internal access would be required.
Why this matters
Why: Buildup can affect airflow/heat response; clear hood with persistent operation needs diagnosis.
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Check 4
Record whether fan runs continuously, grinds, trips power, or smells hot during one controlled observation.
Expected result: Any abnormal noise/odor/trip occurs.
Next step: Stop use and arrange qualified hood/electrical service.
Stop if: Stop if there is a safety hazard or internal access would be required.
Why this matters
Why: The combined pattern exceeds normal heat response.
Use your observations
Decision map
Find the observation that best matches what you see, then follow the next safe action.
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PATH 01Next step
What you see
Fan runs high only while cooking heat is present
Do this next
Let hood cool and confirm return to off/previous setting.
Why this path and its safety boundary
Why it matters: Heat Sentry behavior is plausible.
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PATH 02Next step
What you see
Hood is cool but fan stays on or controls fail
Do this next
Stop modifying settings and arrange service.
Why this path and its safety boundary
Why it matters: Sensor/control/relay/motor issue is more likely.
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PATH 03Next step
What you see
Smoke, burning odor, grinding, or power trip occurs
Do this next
Isolate power safely and obtain qualified service.
Why this path and its safety boundary
Why it matters: Electrical/motor safety issue is possible.
Helpful context
Understand the symptom
How to read the result
If a range hood cycle does not complete, determine whether Heat Sentry is responding to cooking heat or the fan is stuck after cooling. Broan-NuTone says Heat Sentry can run the blower high until temperature drops, then turn off or return to the last setting. A cool hood that ignores controls, smells hot, or makes abnormal noise needs service.
When checks do not resolve it
Need a professional?
Arrange qualified range-hood/electrical service if the fan remains on after cooling, controls fail, motor is noisy, or it smells hot/trips power.
Common questions
FAQ
Why does a hood fan keep running?
Broan-NuTone says Heat Sentry can run it while excessive heat is detected, then return it to off/previous setting.
Can I install a stronger external fan?
No. Broan-NuTone warns against adding one to a hood with its own power unit.
Read the exact guide
Official sources
- Why can’t I turn my range hood fan off?Broan-NuTone · range hood Heat Sentry cycle
- Range Hood FAQsBroan-NuTone · range hood automatic fan behavior
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