A range hood that runs at full speed and still lets smoke roll across the ceiling is almost never a failed motor. It is a restriction — and because the whole system is a single air path, the weakest link sets the performance of everything else. Grease-saturated filters and a clogged blower wheel are the usual culprits, and both are free to fix with an afternoon and some degreaser.
Read this first
- Switch the hood off at the breaker before removing the blower or reaching inside the housing — hoods are frequently hardwired rather than plugged in.
- Blower wheel edges are sharp and coated in solidified grease. Wear gloves.
- Accumulated grease in a hood and duct is a serious kitchen fire hazard, and it is exactly what a weak-airflow hood has been depositing.
- Never vent a range hood into an attic, crawlspace, or wall cavity. Grease-laden air must be ducted outside.
Step by step
Test what you are actually getting
Hold a sheet of tissue paper up to the filter face with the hood on high. It should be held firmly in place. If it flutters weakly or falls, you have very little airflow. Do the same test at the exterior wall or roof cap outside. Strong flow at the filter but weak flow outside means the restriction is in the duct; weak flow at both means it is at the hood or the blower.
Degrease the grease filters properly
Pull the mesh or baffle filters out and hold them up to a light — you should see clearly through mesh filters, and baffle filters should have clean, open channels. A saturated filter is the most common cause of weak airflow and it is invisible from below. Soak them in very hot water with a strong degreaser or dishwasher detergent for twenty minutes, scrub, rinse and dry. Most metal filters are dishwasher safe. Do this monthly on a hood over a range that gets real use.
Replace the charcoal filter if the hood recirculates
If your hood has no duct to the outside — common in apartments and island installations — it filters the air and blows it back into the room through a charcoal or carbon filter. Those are not washable. They saturate in three to six months and then choke the airflow while doing nothing for odour. Find the model number on the hood plate and order the correct cartridge. A hood that has run for years on its original charcoal filter will feel transformed.
Check the backdraft damper
Where the hood meets the duct there is a hinged flap, and there is usually a second one at the exterior cap. Both are supposed to swing freely open with airflow and fall closed when the hood is off. They stick shut with congealed grease, get painted over during decorating, or get bent during installation. Look at each one with the hood running and confirm it opens fully. A damper stuck half open cuts your airflow roughly in half.
Inspect the exterior vent cap
Go outside and look at the wall or roof cap with the hood running on high. Remove any insect screen or mesh — those belong on other vents and they clog solid with grease and lint within months. Check for a bird or wasp nest, a flap held shut by paint, and a cap that has been squashed. This is the single most overlooked restriction in the entire system because nobody thinks to look at it.
Clean the blower wheel
Kill the power at the breaker, remove the filters, and get to the blower wheel inside the housing. On a hood that has never been cleaned you will find every vane coated in a thick layer of solidified grease, which destroys the wheel's ability to move air and unbalances it into the bargain. Many blower assemblies unclip and lift out for soaking. Degrease the wheel, the housing and the intake. This step often doubles the performance of an old hood on its own.
Assess the duct run itself
Look at what the hood is ducted through. Flexible foil duct, undersized duct, long runs, and multiple 90-degree elbows all cost you airflow — a hood specified for a 6-inch round duct will underperform badly on 4-inch, and every tight elbow costs the equivalent of several feet of straight run. If the duct is accessible, replacing flexible sections with smooth rigid metal and easing the bends makes a measurable difference. Also check for a section that has come apart in the ceiling, which sends grease-laden air into the structure.
Consider makeup air
Modern homes are built tight, and a powerful hood cannot exhaust air that the house will not let back in. If a 600-CFM-plus hood pulls noticeably better when you crack a window, you have a makeup air problem rather than a hood problem — and it matters beyond airflow, because a strong hood in a sealed house can backdraft a gas water heater or furnace. Many jurisdictions now require a dedicated makeup air supply above a certain CFM.
What this repair costs
Doing it yourself
$0–$70
Hiring a technician
$150–$500
Prices are general estimates for typical US jobs, not quotes. What you actually pay depends on your appliance's brand and age, the part required, your region, and each shop's labour rate. The DIY figure assumes you supply the labour and buy the part yourself.
Parts you may end up buying
| Part | Install | Typical price | Typical lifespan |
|---|---|---|---|
| Grease Filter | easy | $15–$65 | Wash monthly; replace every 2–5 years |
| Charcoal Filter | easy | $15–$55 | 6–12 months |
| Blower Wheel | moderate | $20–$80 | 10–15 years |
| Blower Motor | moderate | $60–$260 | 10–15 years |
| Speed Switch | easy | $12–$90 | 8–15 years |
| Light Socket and Lamp | easy | $8–$40 | 3–10 years |
| Damper Flap | easy | $10–$40 | 8–15 years |
Still not fixed
When to call a pro
If the filters, damper, cap, blower wheel and duct are all clear and the fan still moves little air, the blower motor is failing — often audible as a motor running noticeably slower or hotter than it should. Motor replacement runs $60 to $180 for the part and is a moderate job on most hoods. Call a professional for ductwork that runs inside a wall or ceiling and cannot be inspected, for any hood that needs to be rerouted or newly ducted to the exterior, and to size and install makeup air. If the hood is hardwired and you are not confident working in the junction box with the circuit confirmed dead, that is an electrician's job.
More range hood guides
- Range Hood Light Not Working — Bulbs, Sockets and Switches15–45 minutes
- Range Hood Won't Turn On — Power, Switch and Control Checks30–75 minutes
- Range Hood Loud or Rattling — Quiet It Down45–120 minutes
- Range Hood Dripping Grease — Fix the Cause, Not the Drip60–150 minutes
- Range Hood Fan Won't Turn Off or Starts On Its Own30–75 minutes
- Downdraft Vent Won't Rise or Lower — Free the Lift45–120 minutes