Damper Bangs When the Wind Picks Up
| Reads like | Actually is |
|---|---|
| Something loose in the ceiling | A flap in the duct with nothing holding it steady — Backdraft Damper |
| A roof or attic problem | A moving part in the vent path, not the structure around it |
| The hood has failed | A hood that behaves perfectly the moment it is switched on |
A noise with no appliance running
Nearly every hood complaint begins with the hood switched on. This one is the opposite: nothing is drawing power and something knocks every few seconds. That narrows the field at once, because the only parts of a vent system that move on their own are the ones hung on a hinge. There are two: the flap in the transition above the blower, and the one outside where the duct leaves.
Nothing holding the flap steady
A working flap rests closed against its frame until the blower has enough behind it to swing it open. What keeps it quiet is contact: a seal, a stop, a little weight. Let any of that wear away and the plate is free to float. The Valley side of this sector hears it most: a ranch house in Valley Village or Sherman Oaks with the blower in the roof has a long vertical run standing open to whatever moves at dusk.
Damper or cap — which one is banging
They sound alike indoors and are put right differently. A knock felt directly above the cooktop, carrying down through the canopy, is the transition flap. A lighter, faster clatter from the wall or the eaves, louder outside than in, belongs to the exterior fitting. Work that out from the kitchen floor and leave the rest to the visit.
What you can look at yourself
- Switch the hood on for a moment. If the knocking stops while it runs and returns once it is off, the flap is the thing moving.
- Watch the vent opening from the ground on a breezy afternoon. A flap rattling out there is a different part from one up in the duct.
- Shut a window on the windward side and listen again. A house being pressurised through one open side works that flap much harder.
- Stop there. Anything behind a panel, above the cabinets or on a roof is the visit — Wolf Repair Los Angeles, (310) 626-4008.
Follow-ups
Can the flap just be taped shut?
No. It is what stops outside air, and everything carried in it, from tracking back down the duct into the kitchen, and it also has to swing clear the instant the blower runs. Held shut, it either tears loose on the next high speed or leaves the hood pushing at nothing.