Backdraft Damper
| What it is | A flap that lets air out and will not let weather back in, set where the duct leaves the hood. |
|---|---|
| Where it sits | In the transition above the blower, where the duct starts |
| How it fails | Bangs in wind, or stays shut, or hangs open and lets cold in |
| Checked with | Opened by hand, then watched with the blower on low and high |
| Price | Quoted after the $89 visit |
A flap that only opens one way
It is the simplest component in the whole system and it decides how the kitchen feels when nothing is running. With the blower on, airflow does all the work of holding it clear. With the blower off, gravity is the only thing closing it, so the hinge has to be free and the blade has to sit flat on its frame. Grease reaches both, because everything the filters miss passes this point.
Shut when it should open, open when it should shut
Stiff, it stays down. The blower roars, the canopy vibrates, and almost nothing leaves the building — a fault that reads exactly like a failing motor and is not one. Hung open, the opposite: a draught over the cooktop on a cold morning, street noise arriving down the duct, and sometimes an insect that found the run from outside. A hood on the slopes above Echo Park feels that side of it sooner, because the duct comes out into whatever the canyon air is doing that evening.
Watched with the blower on low and high
The flap is moved by hand to feel the hinge, then watched through a full run. On low it should lift and stay lifted rather than fluttering against the airstream; on high it should be clear and steady. A blade that chatters at one speed and not the other is usually caught by air coming off the transition rather than faulty itself, and that changes what needs doing.
What putting it right costs
This one has no published band. Wolf Repair Los Angeles puts a figure on it after the diagnosis, as one number covering the part and the labour, and nothing is ordered until you have agreed it — (310) 626-4008.
A flat $89 buys the call-out and a full diagnosis, and that $89 is deducted from the repair once you have approved it.
Follow-ups
Why is there cold air when the hood is switched off?
Something is holding the flap off its seat: grease on the hinge, a screw left standing proud, or a blade warped enough that it no longer lies flat. Wind pressing at the outside cap can hold one up as well. Whichever it is, the duct has become an open pipe into the room.
Can I stop the banging myself?
Not safely in most houses. The damper is inside the duct and the other candidate is the cap out on the wall or roof, and neither is an owner job. What helps is noting whether the noise happens with the hood switched off, which tells Wolf Repair Los Angeles where to start — (310) 626-4008.