Thermador hood running but not clearing smoke

A hood that is loud and useless is describing a resistance problem. The blower is doing what it was told; the air is not going anywhere. There are only three places that resistance can live — the filters, the duct, or the room itself — and you can work out which without tools.

The tissue test

Hold a single sheet of tissue paper flat against the underside of the filters with the blower on high. If it holds firmly, the hood is moving air and the problem is capture — the hood is too high, too shallow for the cooking surface, or the cooking is happening on a front burner outside its footprint. If the tissue barely holds or falls, the hood is not moving air, and the rest of this page applies.

Filters and the blower wheel

Baffle or mesh filters are meant to be washed. Once the mesh is loaded, the free area collapses and the blower spends its energy on noise. Put them through a dishwasher cycle on their own, or wash them by hand in hot water with detergent and a brush — aluminium mesh does not like caustic oven cleaners, and a filter that comes out dulled and chalky has been attacked rather than cleaned.

Behind the filters, look at the blower wheel with a torch. Grease builds on the blades as a thick, even coating, which both adds weight and destroys the blade profile. A loaded wheel is the classic cause of a hood that got gradually quieter in effect and louder in sound over several years.

The duct and the damper

Go outside and look at the wall or roof cap while someone runs the hood. The damper flap should lift. Caps in this climate collect grease at the hinge and seize shut, and they also make attractive nesting sites; either way, the blower runs against a closed door.

Inside, the duct matters more than most owners expect. Flexible duct has several times the resistance of smooth rigid pipe of the same diameter, and every bend costs more. A run that was reduced from the hood’s outlet size to fit a joist bay — a common shortcut in the 1980s and 1990s houses around Pace Island and older Fleming Island streets, where the kitchen was rebuilt long after the frame went up — will throttle any blower you fit to it.

The house itself

This is the cause nobody looks for. Every cubic foot of air a hood exhausts has to be replaced by a cubic foot entering the house. Newer construction in Oakleaf Plantation is built tight, and a high-capacity hood over a professional rangetop can easily ask for more air than the envelope will give up. The result is a hood that pulls fine with a window cracked and pulls nothing with the house closed up.

Test it directly: open a window in the same room, run the hood, and see whether performance changes. If it does, the appliance is healthy and the installation needs a makeup air path. That is a building problem with a building solution, and no amount of blower replacement will fix it.

A related tell is a gas appliance elsewhere in the house whose flame pulls or flickers when the hood runs. Take that seriously and stop running the hood at high speed until the makeup air question is settled.

Recirculating installations

If the hood was installed without a duct to outside, it is filtering and returning air to the room, and it depends entirely on a charcoal cartridge that has a service life measured in months. Those cartridges are frequently installed once and never changed. A recirculating hood with a spent cartridge removes essentially nothing, which matches the complaint exactly.

Booking

The flat $80 diagnostic covers checking the blower, the controls, the damper and the duct termination, and telling you plainly if what you have is an installation problem rather than an appliance problem. Written estimate before any work begins, fee credited toward the repair, genuine OEM parts, 90 days on labor and 365 days on parts.