At a glance
Symptoms
- • Smoke and steam linger over the cooktop instead of being pulled up
- • Cooking smells fill the rest of the house
- • Greasy film building up on cabinets near the stove
- • Hood is noticeably louder than it used to be at the same speed
- • Visible airflow at the bottom of the hood is weak or absent
- • Outdoor vent flap is not opening when the hood runs
- • Lights work fine but suction is poor
Common causes
- • Clogged grease filter — most common single cause (mesh or baffle filter)
- • Saturated charcoal filter (ductless / recirculating models only)
- • Clogged or grease-coated ductwork
- • Stuck or damaged exterior vent damper
- • Ductwork run too long, with too many bends, or undersized diameter
- • Hood physically undersized for the stove (CFM rating too low)
- • Fan motor degraded or seized
- • Backdraft damper inside the hood stuck closed
Safety First — Read Before You Start
- •Turn off the hood and cooking surface before removing filters or accessing internals.
- •For wired hoods, turn off the breaker before any internal work beyond filter cleaning.
- •Allow at least 30 minutes after cooking before cleaning — grease filters can be hot enough to burn.
- •When checking the exterior vent on the roof or outside wall, use a stable ladder with a spotter. Never work on a roof in wet conditions.
- •Do not put grease filters in the dishwasher with food dishes — heavy grease can clog the dishwasher pump.
- •Charcoal filters cannot be cleaned and reused. They must be replaced.
Tools & supplies you'll need
- Phillips screwdriver
- Degreaser (commercial kitchen degreaser or hot water + dish soap + baking soda)
- Soft brushes
- Replacement charcoal filter (for ductless models)
- Replacement grease filter if old or damaged
- Ladder
- Flashlight
- Anemometer or candle (to test airflow)
- Vacuum with brush attachment
Step-by-step instructions
Pull and clean the grease filters
Most hoods rely on either wire mesh or aluminum baffles to catch grease. Remove them using the pull-tabs or spring clips. If you cannot see light clearly through the material, it is obstructed. Soak these in a mixture of hot water, dish soap, and 1/4 cup of baking soda for up to 30 minutes. Scrub gently with a soft brush. If they are severely coated, you may need a second soak. Ensure they are dry before putting them back. This simple cleaning often restores full suction power.
Tip: While aluminum mesh is dishwasher-safe, wash it separately to prevent grease from coating your dinnerware. Replace mesh filters every 2-3 years; baffles typically last 5-10 years.
⚠ Warning: Never operate a hood with blocked filters, as grease buildup inside the fan housing creates a significant fire hazard.
Identify ducted vs. ductless and check the ductwork
Determine if your system is ducted (venting outside) or ductless (recirculating). Ducted units have visible metal piping. Inspect this path for kinks, heavy grease deposits, or sagging sections. If the duct is too small or has too many 90-degree turns, it will choke the airflow regardless of how powerful the motor is.
Tip: A 6-inch duct moves substantially more air than a 4-inch duct. If your setup was restricted to fit a smaller pipe, the hood will never reach its full CFM potential.
⚠ Warning: N/A
Replace the charcoal filter (ductless models)
Ductless hoods rely on charcoal filters to scrub odors. These are not washable and must be replaced every 3-6 months for heavy usage or 6-12 months for lighter use. They are typically held in place by clips or twist-locks behind the grease filters. If your kitchen smells like your last meal, it is time for a new filter.
Tip: Frequent high-heat searing or frying will saturate these filters faster than boiling water or steaming vegetables.
⚠ Warning: N/A
Test and clear the exterior vent damper
The exterior vent flap should open easily when the hood is running. If it is stuck due to grease or debris, your hood is essentially blowing against a wall. Check the roof or exterior wall vent cap. Ensure it is free of lint and that no decorative screens are blocking the exit. Use a long tool or rag to clear any buildup.
Tip: N/A
⚠ Warning: Always use a secure ladder and have someone assist you. Avoid roof work during the rainy weather common in the PNW.
Check the internal damper
Look inside the hood housing for the internal backdraft damper—a flap that pivots open when the fan is on. If grease has glued it shut or it has shifted, airflow will be severely limited. Clean it with a degreaser so it moves freely.
Tip: N/A
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Test the fan motor
If everything else is clear, the motor might be failing. Listen for grinding noises or a lack of change in pitch between speeds. A simple 'paper test'—holding a sheet of paper against the hood—should show strong suction if the motor is healthy. If the motor is faulty, it will need to be replaced.
Tip: If you have a single-speed motor that feels weak, check the start capacitor first. It is a much cheaper and easier fix than replacing the entire motor.
⚠ Warning: N/A
Confirm the hood is correctly sized for the stove
Sometimes the issue is simply that the hood is too small for the cooktop. A general rule is 100 CFM per linear foot of stove width. A 36-inch range requires at least 300 CFM. If you have a high-output burner, you may need 600+ CFM. If your hood is undersized, no amount of cleaning will fix the lack of draw.
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⚠ Warning: N/A
Brand-specific notes
Some brands have known design quirks worth knowing about before you start.
Broan / NuTone
These are common in many PNW homes. The QS series is standard; parts like dampers and motors are easy to source and replace. If the unit is over 8 years old, the motor capacitor is a frequent failure point.
Vent-A-Hood
These use a unique 'Magic Lung' system. There are no traditional filters; instead, grease is collected in a cup. If suction is poor, clean the impeller and the grease cup, but be careful not to damage the bearing seals with harsh chemicals.
Zephyr
These are high-quality units. Weak suction usually points to a blocked external vent or a stuck internal damper rather than motor failure.
Bosch
These feature precision baffles that require regular cleaning. Most models have a built-in indicator light; if it is illuminated, it is time to clean or swap the filters.
Faber
Even ducted Faber models use charcoal filters for odor control. Owners often forget to replace these, leading to restricted airflow over time.
GE / Whirlpool
For over-the-range microwaves, ensure the unit was configured for 'vented' rather than 'recirculating' during installation. If the vent is set incorrectly, it will never pull air effectively.
What our techs see most often
Most of our calls for weak range hood suction are resolved by simple maintenance. About 60% are just dirty grease filters, 15% are saturated charcoal filters, and 15% relate to ducting or exterior vent obstructions. Only about 10% involve actual motor or electrical failure. In the Pacific Northwest, we frequently see modern, high-CFM hoods installed on old, undersized 4-inch ducts, which causes significant performance issues.
When to call a professional
- → Filters are clean, ducts are clear, dampers move freely, and suction is still weak
- → Fan motor is making grinding or burning-smell noises
- → You suspect ductwork was incorrectly run during installation (long runs, multiple sharp bends, undersized diameter)
- → The hood is on a roof exit and the cap, flashing, or pitch needs to be inspected
- → You smell electrical burning from the hood
- → The hood is a high-end built-in (Wolf, Thermador, Miele) where DIY motor work may void warranty
- → Grease has accumulated heavily inside the duct over years of poor maintenance — duct cleaning is a specialized service
Range Hood Maintenance & Replacement Tasks
Step-by-step guides for individual maintenance jobs related to this appliance.
Frequently asked questions
How often should I clean my range hood grease filter?
For light cooking, aim for every 2-3 months. For regular use, make it a monthly task. If you do a lot of frying, clean them every 2 weeks. A clogged filter strains the motor and reduces efficiency.
Are charcoal filters in ductless hoods worth it?
They help with odors but won't manage steam or heat like a ducted system. They are necessary for ductless setups, but remember they are consumables that require replacement every 3-12 months.
How big a range hood do I need?
Plan for 100 CFM per linear foot of stove. High-output gas ranges often require 600-1200 CFM and may need a makeup air system to prevent the hood from fighting negative pressure.
Why does my hood seem weaker in winter?
Cold, dense air can exert pressure on the exterior damper, and tightly sealed homes can create negative pressure. Cracking a window slightly can help the hood draw air more effectively.
Is it safe to use a range hood with weak suction?
It is not ideal. Beyond the lack of smoke removal, it allows grease to build up on your kitchen surfaces and inside the ducting, which is a significant fire hazard.
Related Repair Guides
Troubleshooting a Range Hood Fan That Won't Run
If your range hood lights are operational but the exhaust fan refuses to spin, you are likely dealing with a localized circuit failure. Because the lighting and fan motor systems often share a power source but utilize independent control paths, the issue usually boils down to a faulty switch, a failed capacitor, a worn-out motor, or a glitchy control board. Most of these repairs can be completed for under $80 in parts.
How to Clean a Range Hood Grease Filter
Keep your kitchen air crisp and your ventilation system efficient. Cleaning your range hood filter is a quick, manageable task that prevents motor strain and keeps your home smelling fresh.
Range Hood Light Not Working: Troubleshooting Guide
Struggling to see your stovetop because your range hood light is out? This is a frequent issue for many PNW kitchens. Whether you are dealing with a simple bulb burnout, grease-clogged controls, or a transformer failure, this guide will walk you through the diagnostic process safely.