Ventilation and hood repair

Ventilation is the category where the complaint and the fault are furthest apart. Almost nobody calls about a hood because a component failed; they call because the kitchen fills with smoke. Those are different problems, and the second one frequently has nothing wrong with it electrically.

When the blower will not start

A blower that hums without turning is a motor that is being energised and cannot break away. On a single-phase motor that is either the start capacitor or a mechanical bind, and the two are easy to separate: cut the power, and try to turn the wheel by hand. A wheel that spins freely with a hum on power points at the capacitor. A wheel that will not turn is bearings or an obstruction.

A blower that only works on one speed is the control side, not the motor. Speeds are switched, and losing the intermediate positions while the top speed still works means the switch or the control board is dropping the taps that make the lower speeds.

Note where your blower physically sits, because it changes the job entirely. Some hoods carry the blower in the canopy; others use an in-line blower in the attic or joist space, or a remote blower mounted outside the house. On a house with an in-line unit, the hood on the wall may be perfectly healthy and the thing that failed is thirty feet away above the ceiling. If you know which kind you have, say so when you book.

Noise and vibration

Hood noise almost always increases gradually, which is why people stop noticing it until it becomes intolerable. The usual cause is the blower wheel loading up unevenly with grease. A wheel is balanced when it leaves the assembly line; a few years of frying puts a heavy deposit on some blades and not others, and an unbalanced wheel at speed shakes the whole canopy.

Cleaning the wheel restores the balance and it is a maintenance job, not a repair. A wheel that stays noisy after cleaning has usually taken its bearings with it.

Filters matter more than they appear to. Baffle filters that are not washed on a schedule pass grease straight into the blower and the duct, which is what creates the wheel problem in the first place and, separately, is the thing that turns a duct run into a fire risk.

Smoke that will not go up

This is the complaint that is usually not a fault. Capture depends on three things, and the blower is only one of them.

The first is duct. Every elbow, every foot of run and every transition to a smaller size costs airflow. A hood ducted straight up and out through a short run performs close to its rating. The same hood pushed through a long horizontal run with several turns to reach a wall on the far side of the house does not, and no amount of extra blower will recover it.

The second is the termination. Roof caps and wall caps have backdraft dampers, and dampers seize. A damper that no longer opens fully throttles the entire system at its last six inches. On the waterfront lots along Doctors Lake and the river we also see dampers that chatter in a sustained onshore breeze and, over years, wear their hinges out. That is also the source of the cold draught people report coming down through a hood that is switched off — a damper that no longer closes.

The third is makeup air. A tight modern house running a large blower with every window shut has to get replacement air from somewhere. If it cannot, the blower is fighting a pressure difference and moves far less than its rating. Cracking a window near the kitchen and seeing the capture improve is a diagnosis, not a coincidence.

Lights and controls

Hood lights that flicker when the blower runs point at a shared supply or a loose connection rather than the lamps. Lights that are simply out are usually the lamp or the socket, and on the models that use a transformer, that transformer.

Controls that are entirely dead while the blower still runs audibly on its last setting are the control board — and in this region, that is worth dating. A hood board that died the same week as a storm has almost certainly been through a power event, and it is worth checking what else in the kitchen was on the same circuit before assuming it failed of old age.