A range hood is the appliance most kitchens take for granted. Until cooking gets smoky and the smoke just hangs there. When the hood runs but doesn’t pull air, the cause is almost always one of three things. Here’s how to work out which.
1. Clogged grease filters
The metal mesh filters at the bottom of the hood catch oil droplets. They work. Until they’re saturated. A grease-loaded filter restricts airflow more than people realise; the motor still spins normally but moves a fraction of the air.
What to do. Slide out the filters (most click out). Hold one up to the light. If you can’t see through it, it needs cleaning.
Two cleaning methods that work:
- Dishwasher. Top shelf, normal cycle. Works for most metal filters. Some manufacturers warn against this on coated aluminium. Check your manual.
- Hot soapy soak. Sink full of hot water + dish soap + a tablespoon of baking soda. Soak the filters for 30 minutes, scrub with a stiff brush.
Air-dry fully before refitting. Set a quarterly reminder. Filters that go more than 6 months between cleans rarely come back to full performance.
2. Charcoal filter exhausted (recirculating hoods only)
If your hood doesn’t vent outside (no duct through the roof or out the wall), it’s a recirculating model. It uses a charcoal filter to absorb odours before pushing the air back into the kitchen.
Charcoal filters are NOT washable. They’re saturated when they look saturated. Typical replacement is every 6 months for a kitchen used daily.
What to do. Locate the charcoal cartridge (usually behind the grease filter, sitting against the back of the hood). Remove and inspect. If it looks brown / dirty / smells stale, replace.
Replacement filters are brand-specific. Bring the old one to the appliance store, or order from the manufacturer.
3. Failed motor or capacitor
If filters are clean, ducting is clear, and the hood still doesn’t pull air. The motor or its run capacitor has gone.
Symptoms of motor failure: the fan spins very slowly, makes a low hum, or doesn’t spin at all even though the light works (the two circuits are usually separate).
Symptoms of capacitor failure: the motor starts but quickly gets weak, or runs at only one speed regardless of the switch setting.
What to do. Book a service call. Motor and capacitor diagnosis needs voltage testing and access to the motor housing.
4. Blocked ducting (ducted hoods only)
If your hood vents outside, the duct itself can clog with grease over years. The fan motor and filters are fine but the air has nowhere to go.
What to do. Look at the external vent (usually on the roof or the side of the house). Is it clear? Is the flap free? Inside, the duct itself may need a clean. That’s usually a job for a duct cleaner, not an appliance technician.
Light works but fan doesn’t
The light and the fan are usually on separate circuits. If the light works but the fan doesn’t switch on at all, the fan switch or motor is the suspect, not the power supply. Skip ahead to step 3.
When to call
Filter and charcoal cleaning is DIY. Motor and capacitor faults need a technician. Ducted blockages may need a duct cleaner first. We can advise on the visit if that’s where the problem lies.