Home/Everyday/Blind cord jammed

A cord lock is a wedge. Pulling harder is exactly what is holding it.

The cord will not move at all · It went an inch and then locked solid · It jams at the same height every time · One side rises and the other does not · The blind hangs crooked · It happened after someone pulled it hard · The cord feels slack but nothing happens · A cord has jumped off something at the top · The cord is frayed near the lock
FreeLift the rail to slacken it, then pull gently
FreeWork a knot out at one slat — do not cut the cord
BoughtA new cord or lock, only if the cord has snapped
Lift, then pull Why pulling tightens it
Easy · 15 min · Two of the three answers are free, and the first is the opposite of what you are doing

A venetian blind at a window with its headrail across the top, twelve slats hanging below it, a bottom rail and a pull cord with a handle at the right; the lock sits inside the right end of the headrail and a small pulley shows above it; below left, the cord lock in section — a tapered shell with a wedge dragged down against the cord, and a spring behind it; below right, two small panels comparing a downward pull, which grips, with lifting the rail, which releases

diagnose
What failed
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Where
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State
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what to touch fault correct Click the blind, a slat, the lock or the pulley

The lock grips in proportion to the pull — so the harder you pull, the more stuck it is

One fact about the mechanism explains the whole page. A cord lock is a wedge sitting in a tapered shell, and the cord drags it towards the narrow end. The narrow end is smaller than the cord, so the wedge presses the cord against the shell, and the harder the cord is pulled the further the wedge is dragged and the harder it grips. This is called self-locking, and it is not a fault — it is the entire design. Without it the blind would fall down the moment you let go.

Which means the state you are in is the state it is built for. Something pulled that cord hard — a child, furniture being moved, a window that caught the blind — and the wedge went deeper than a normal pull takes it. Now every pull you add drives it further in. The release is the opposite direction: push the bottom rail up a couple of centimetres. That takes the tension off the cord, the wedge is no longer being dragged, a weak spring (or gravity, on cheaper locks) walks it back up the taper, and the cord is free again. Then pull gently, straight down, without a snatch.

Notice what that test is doing. It is not a fix, it is a measurement. If lifting the rail frees the cord, then the whole mechanism is intact — the lock, the wheel, the cords and the slats are all working, and you have learned that without taking anything apart. If lifting the rail changes nothing, the cord is being held somewhere else entirely: knotted at a slat, off the wheel, or no longer attached to the blind at all.

Three faults, three places

It frees when you lift the rail is the lock, and it needs no part. Once it runs, set the lock so it grips on a light pull and releases on a lift: most locks have a small screw or a sliding cover that changes how much of the taper the wedge can travel. Do that with the blind at half height, testing as you go, because too loose and the blind creeps down on its own overnight.

It stops at the same height every time, and that height moves with the slats is a knot or a crossing in the cord at one slat. Work the cord slat by slat from the bottom, watching each hole as the blind passes it, and you will see the tangle. Free it with a bent paperclip or a blunt needle — never cut the cord to remove a knot, because a cut cord has to be replaced and the knot does not. Then straighten the slats so the cords run parallel through every hole before you run it.

The cord pulls with no resistance at all, or will not pull and hangs loose is the top of the blind. The cord has come out of the groove of the pulley inside the headrail, so it is binding on the metal edge rather than turning. Take the end cap off — usually one screw or a clip — look in with a torch, and press the cord back into the groove with a flat screwdriver. Then run the blind fully down and fully up to re-tension both sides before you trust it.

Three rules, and the second one is the reason a lubricated blind falls down on its own. Never yank, and never tug in short bursts. Each tug drives the wedge deeper; the version of this fault that needs a new lock is almost always made by trying harder. Never put oil or silicone on the cord. This is the one mechanism in the house that works because of friction — a door lock is the opposite and does need it. Lubricate this and the blind will not hold its height at all. If the cord is frayed, or the blind is older than the cords, stop. A frayed cord cuts hands, chews a groove in the wedge so it can never grip properly again, and a hanging cord loop is a strangulation risk for small children. Replace the cord, or fit a tensioner so the loop cannot form.

Faults next to this one

Door stop not holding A magnetic door stop does not hold the door, it parks it at an angle. Peephole blurry or loose A door viewer is two lenses in a tube, clamped by the ring on the inside. Window not closing tight A window seals because the lock points pull the sash onto the frame and squash the gasket.