Repair or Replace a Lock? How to Decide

In short:

Check the door before blaming the lock. Sagging hinges and a moved frame put strain on the lock and make it feel faulty.
Wear, dirt and a misaligned strike plate are usually repairable. A cracked case, bent bolt or forced cylinder usually isn't.
If you can't account for every key, the question isn't really repair or replace: the keyed part has to change.
On euro-profile locks the cylinder can often be swapped on its own, keeping the rest of the lock.
The technician quotes on site for both options, and nothing is done until you choose.

Rule out the door first

Many "faulty locks" are healthy locks fitted to a door that has moved. ASSA ABLOY South Africa's care guide points out that faulty hinges, warped doors and distorted frames put excessive load on other components and shorten their life. If the door has dropped even a few millimetres, the bolt rubs on the strike plate, the key has to fight the bolt, and the lock gets blamed.

A simple, safe test:

Open the door fully so the lock is clear of the frame.
Turn the key or thumbturn and work the handle a few times.
Close the door and try again.

If everything is smooth with the door open but stiff with it closed, the lock is probably fine and the door, hinges or strike plate need attention. If it's stiff either way, the lock itself has a problem. Note which one you found; it's the first thing a technician will want to know.

Faults that are usually worth repairing

Repair makes sense when the lock is sound and the trouble is wear, dirt or adjustment. Typical examples:

A stiff or gritty key action in a lock that is otherwise in good order. ASSA ABLOY's guide recommends lubricating key cylinders at least once a year, or when the key starts to feel rough, using graphite powder for cylinders, lever locks and padlocks, and avoiding silicone-based lubricants, which turn tacky. Other makers give different advice for their own cylinders, so follow the guidance for your brand.
A strike plate that has drifted out of line with the bolt or latch.
A loose handle or rose where the fixings have worked free.
A weak latch spring or a handle that doesn't return, on a lock where the spare part is available.
Corrosion on the outside from weather or dirt that hasn't yet reached the mechanism.

The common thread: the parts that keep the door locked are intact, and you trust everyone who holds a key.

When replacement is the better answer

Replacing the lock, or at least its keyed part, is usually the right call when:

Keys are unaccounted for. Lost keys, a tenant or staff member who left without returning theirs, a new home where you don't know who else has one. No repair changes who can open the door.
It was damaged in a break-in. A cracked case, a bent bolt, a cylinder that has been attacked or a twisted handle shouldn't be trusted again, even if it seems to work.
It keeps coming back. A lock that has needed attention several times is telling you something.
Parts aren't available. Older or unbranded locks often have nothing to repair them with.
You want more security than the lock was ever designed for, for instance a higher-lever lock or a better cylinder on an outside door.

Common situations and the usual outcome
Situation	Usual outcome	Why
Stiff only when the door is closed	Adjust the door or strike	The lock is working; the door is loading it
Rough key action, lock otherwise sound	Clean and lubricate per maker	Dirt and dryness, not failure
Keys lost or not returned	Replace the cylinder or lock	Only a new keyed part changes who can open it
Damage after forced entry	Replace	Damaged parts can fail later without warning
Same fault for the third time	Usually replace	Wear has gone beyond adjustment
Wanting better security	Upgrade	A repair keeps the old lock's limits

The middle option: change only the part that's failing

A lock is several parts working together, and they don't all wear out at once.

Illustration The main parts of a typical door lock (not to scale). Lever locks have no separate cylinder, so the keyed part and the case are one unit.

On a euro-profile lock, the cylinder is the keyed part, and it can be changed without altering the rest of the lock mechanism. That makes it the natural fix when keys go missing or the cylinder wears, while a healthy lock case stays in the door. On a lever mortice lock, the keyed parts are inside the case, so a change of keys usually means a change of lock.

Handles, roses and strike plates can usually be dealt with separately too. Replacing only the failing part is often the most sensible outcome, as long as the rest of the lock is genuinely sound.

Choosing a replacement that suits the door

If replacement wins, the new lock has to fit both the door and the risk:

Same size and type, so it fits the existing cut-out without weakening the door. Mixing sizes means extra cutting.
Lever count on mortice locks. UNION's Gower range sold in South Africa comes in two-, three- and four-lever versions and euro-profile versions, all listed as SABS approved. Outside doors deserve more than the minimum.
A better cylinder where it matters. For euro-profile locks on outside doors, see our article on anti-snap cylinders for what the ratings mean.
Your insurer's wording. Policies set their own security conditions. Read yours before choosing.
How many keys you want to carry. Some cylinder ranges come in keyed-alike sets, so several doors can share one key.

Habits that turn a repair into a replacement

Forcing the key. A key that needs effort will eventually snap or bend. If it happens, our guide to a broken key stuck in the lock explains what to do next.
Spraying oil or a household spray into the keyway. ASSA ABLOY's guide calls for graphite powder in cylinders and lever locks, and warns that too much lubricant holds dust on the parts.
Using pliers or a bar on the handle to get more leverage.
Slamming the door to make the latch catch, instead of fixing the strike or hinges.
Taking the lock apart without the maker's instructions. Small springs and levers are easy to lose and hard to refit.

What helps the technician quote on site

You'll get a clearer answer, faster, if you can share:

photos of both sides of the door, and the faceplate on the door edge;
the result of the door-open test above;
the brand of the lock, if it's marked;
whether all keys are accounted for;
whether the lock was forced or damaged;
whether other doors share the same key.

Our lock replacement service covers new locks and cylinders, and lock repair covers fixes that keep your existing hardware. If the trouble followed a forced entry, break-in repairs is the place to start. As a Boksburg mobile locksmith we come to you, 24/7. There's an R250 call-out, and the technician quotes on site before any work starts, for repair, replacement or both, so you can choose. Payment is by EFT, cash or card.

Questions

Is repairing always cheaper than replacing?

Not always. A repair on a worn lock can be followed by another one, and an inexpensive cylinder swap can beat a long repair. That's why the technician quotes on site for the options before starting.

Can my new lock work with my old key?

No. We don't cut or copy keys, and a new lock or cylinder comes with its own keys from the maker. If you want several doors on one key, ask about keyed-alike cylinders when the locks are replaced.

Do I need to change the locks after moving into a new home?

If you can't be sure who else holds keys, such as previous owners, tenants, agents or contractors, changing the keyed parts is the only way to be certain. On euro-profile locks that often means new cylinders rather than whole new locks.

Need a locksmith to look at it?

If this hasn't solved the problem, our lock replacement service covers it. We're a mobile locksmith in Boksburg, so we come to your door.

Sources and further reading

ASSA ABLOY South Africa: Product care and maintenance (PDF) — faulty hinges, warped doors and distorted frames load other components; lubricate cylinders at least annually or when rough; graphite powder for cylinders, lever locks and padlocks; avoid silicone-based lubricants
Wikipedia: Euro cylinder (pin tumbler lock types) — profile cylinders can be changed without altering the boltwork
ASSA ABLOY South Africa: UNION locksets — Gower two-, three- and four-lever and euro-profile locksets, listed as SABS approved
ASSA ABLOY South Africa: Mzansi CYS00 double euro cylinder — locally sold cylinder supplied with keys and available keyed to differ, keyed alike or in master-key systems