Chimney-style range hood with a glass canopy over a cooktop
Generic photo: Bilguun Gantumur · Pexels License

Field pattern: range hood 'weak suction, needs a new motor' (filters, damper, duct and cap first)

Weak capture on a hood whose fan runs is usually airflow restriction: loaded filters, a damper that does not open (shipping tape on new units), an undersized or long duct, a crushed flex section or a blocked exterior cap. Cosmo's tissue test with the duct on and off separates the hood from the installation in minutes.

Cross-checked ~45 min easyBrands: All

Before you start

  • Unplug or switch off the hood before removing the chimney, duct or filters
  • Support the hood when disconnecting the duct

Diagnostic steps

Unlock all 7 steps with expected values

Full library + AI assistant + the OnCall Tech app for iPhone & Android. $34.90, one time.

Get lifetime access

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.

More range hoods guides

Guide · Range Hood

Range hood fan runs only on high, runs slow, or a speed is missing

On simple switch hoods, a missing speed is usually the switch or a failed winding tap; on board-controlled hoods it can be a relay on the control. A fan that is slow on every speed points to grease-dragged bearings, a weak run capacitor on PSC motors, or airflow restriction. Check mechanical drag and airflow before electrical parts.

8 steps ~45 minmoderate
Guide · Range Hood

Cold air, odors or insects coming in through the range hood when it's off

Two dampers should block the duct when the fan is off: one at the hood and one in the wall or roof cap. Grease, bends, missing springs or screws in the path keep them open. Long duct runs and a house under negative pressure make it worse. Fix the dampers first; make-up air questions go to code and an HVAC or licensed contractor.

7 steps ~60 minmoderate
Guide · Range Hood

Range hood grease filters: cleaning baffle and mesh filters (and when to replace)

Loaded grease filters cut airflow and can make the motor overheat. Identify the filter type, clean stainless baffles and mesh with hot water and a degreasing soak or the dishwasher where the maker allows it, never put charcoal filters in water, and reset the hood's filter reminder.

7 steps ~30 mineasy
Field pattern: range hood 'weak suction, needs a new motor' (filters, damper, duct and cap first) · OnCall Tech