Deadbolt Won't Lock or Turn? Find Out If It's the Door

Most deadbolts that will not lock are not broken. The bolt is hitting the edge of the strike plate because the door has sagged, swelled or shrunk, and the fix is at the hinges or the strike, not inside the lock. To find out which you have, open the door and turn the key or thumbturn. If the bolt slides out and back smoothly with the door open but sticks with it shut, the door is out of line. If it is stiff even with the door open, the lock itself needs attention.

The open-door test, step by step

This takes a moment and saves a lot of guessing.

Open the door and work the thumbturn. Throw the bolt all the way out and back a few times. Note how it feels.
Step outside, door still open, and use the key. Same thing. Some faults only show from one side.
Watch the bolt. It should come out its full length, usually about an inch, and stop firmly.
Close the door and try again. Then try once more while pushing the door firmly into the frame, and once while lifting the handle slightly.

What the results mean:

Smooth open, stiff shut. Alignment. The bolt is rubbing on the strike or the hole behind it.
Locks only when you push or lift the door. Alignment, and the direction you had to move the door tells you which way it is off.
Stiff open and shut. The lock. A worn or dirty cylinder, or a bolt mechanism that is binding or broken.
Thumbturn works, key does not (or the other way round). The connection between the two sides, covered below.

Finding where the bolt hits

Rub a little lipstick, chalk or dry-erase marker on the end of the bolt. Retract it, close the door, and turn the lock gently until the bolt touches something. Open the door and look at the strike plate.

A mark below the hole means the bolt sits lower than the opening. The door has dropped on the latch side, or the strike was set too high. This is the common one.
A mark above the hole means the bolt sits higher than the opening. The strike was set too low, or the latch side of the door has risen, which happens less often.
A mark beside the hole means the door sits too far in or out in the frame, often from new weatherstripping or a frame that has moved.
No mark on the plate, but the bolt stops short means the bolt goes into the hole and hits the bottom of it. The hole in the jamb is too shallow.

The gaps around the door tell the same story. A gap that is wide at the top on the latch side and tight at the bottom is a classic sag.

Why doors move

Doors that worked for years do not usually stop working all at once. Something shifts slowly until the bolt finally catches.

Loose hinge screws. The top hinge carries most of the weight of the door. When its screws loosen in the jamb, the latch side drops.
Swelling and shrinking. Wood takes on moisture in humid weather and dries out once the heat is on indoors. A bolt that lines up in one season can bind in the other.
New weatherstripping. A thick seal pushes the door outward in the frame, so the bolt meets the plate off centre.
A settling house or an old kick. Frames move. A door that was forced in the past may have a jamb that never quite went back.

Fixes you can try, and where to stop

Start with the hinges, because they are the cause most often and the fix is cheap.

Tighten every hinge screw. If a screw in the top hinge spins without biting, replace one of them with a screw long enough to reach the framing behind the jamb, about three inches. Drawing the top hinge in tight often lifts the latch side back into line. Do not overdrive it, or you can pull the frame the other way.
Ease the strike opening. If the mark is just a few millimetres off, filing the inside edge of the strike opening can be enough. File the plate, not the bolt.
Deepen the hole. If the bolt bottoms out, the hole behind the strike needs to be drilled deeper.

Stop when the fix means moving the strike plate more than a little, chiselling the jamb, or planing the door. Moving a strike means filling the old screw holes and cutting a new recess, and a strike screwed into patched wood is easy to kick through. Our deadbolt installation guide explains the strike, screw lengths and hole depth in more detail.

Two things not to do. Do not spray lubricant into the lock to cure an alignment problem: it will not help a bolt that is hitting wood or metal. And do not force the key. Leaning on a key against a bolt that is binding is a common way for keys to snap off, and then you have the problem in our post on a key broken in the door lock as well.

When it is the lock, not the door

If the open-door test pointed at the lock, here is what is usually behind it.

A worn or dirty cylinder. The key goes in but turns roughly, or only with jiggling. Old pins and springs wear, and grit collects in the keyway.
Over-tightened mounting screws. On a standard deadbolt, the two screws that hold the inside and outside halves together can squeeze the bolt mechanism if they are cranked down too hard. Back them off a quarter turn and test again. If that cures it, you have found the problem.
A misaligned tailpiece. The flat bar that runs from the cylinder through the bolt mechanism to the thumbturn has to sit in its slot the right way. After a lock has been taken apart, it can go back in at an angle, so one side turns and the other spins or does nothing.
A broken part. A key that turns all the way with no effect on the bolt, or a bolt that slides back in when you push it, usually means a broken cam, tailpiece or bolt mechanism.

The last two are repair-or-replace questions. If the deadbolt is old, worn and a low grade to begin with, replacing it is often the better choice. Larchmont Locksmith NY repairs and replaces deadbolts as part of our residential lock service, and service starts at $125.

Older doors in Pelham and Larchmont

Both places have plenty of older houses with heavy wood front doors, and those doors are where alignment trouble shows up most. Solid wood moves more with the seasons than a modern steel or fibreglass door. Frames have had decades to settle. And many older doors carry mortise locks, where the deadbolt sits inside a rectangular case in the door edge. The same test applies to a mortise deadbolt: if it throws freely with the door open, look at the strike and the hinges before suspecting the lock.

In the Town of Pelham, which takes in the villages of Pelham and Pelham Manor, our third technician lives at the edge of the Bronx, close by. Two of our technicians live in Larchmont, so the village is home ground. See our Pelham locksmith page or our page for lock repair in Larchmont.

Frequently asked questions

Why does my deadbolt only lock when I push the door?

Because pushing the door moves the bolt into line with the hole in the strike. The door or the strike has shifted, usually from loose hinge screws or seasonal swelling. Tightening the top hinge or easing the strike opening often fixes it.

Should I spray WD-40 into a deadbolt that will not turn?

Not as a fix. Household oil and spray lubricants collect grit and can gum up the pins over time. If the lock is stiff even with the door open, a puff of graphite or a dry PTFE lock lubricant is the better choice. If the problem is alignment, no lubricant will help.

Is a deadbolt that will not fully extend still secure?

Not fully. Many deadbolts only lock firmly in place when the bolt is all the way out. A bolt that stops halfway can sometimes be pushed back from outside. Fix the strike or the hole depth so it throws its full length.

Can I adjust the strike plate myself?

A small adjustment, yes: filing the edge of the opening or tightening loose screws. Moving the strike to a new position is harder to do well, because the new screws need solid wood and the old holes need filling.

If your deadbolt still will not turn, call Larchmont Locksmith NY at (914) 255-6611 any hour.