The Safe That Opens for the Wrong Combination
A small business owner reports that a used TL-15 rated safe, purchased at auction, opens with the combination written on a tag inside the door - but also, on roughly one out of five attempts, with a combination that is one number off on the third dial position. The dial is a standard three-number mechanical group-2 style lock. The owner wants you to 'just change the combination' to something only she knows. You have not yet inspected the lock, the boltwork, or the door-mounted relocker. The safe is currently open. The owner is impatient and says the safe 'has always done that' and it has never been a problem.
1. What does the intermittent 'one number off' behavior most likely indicate, and why can you not simply proceed to a combination change?
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An intermittent open on a near-miss third number is a classic symptom of a worn or misaligned wheel pack / drive mechanism - for example a loose drive cam, a worn wheel that has developed a false gate, a stretched or slipping drive pin, or a fence that is seating on a wheel edge rather than in the true gate. It can also indicate the dial-to-spindle relationship has slipped so the indexed numbers no longer correspond to the actual gate positions.
The reason you cannot just change the combination: a combination change assumes the lock is functioning correctly and that the new combination will be the only one that opens it. If the wheel pack has a false gate or the drive has slipped, a new combination will inherit the same defect - the safe will still open on near-misses, and worse, the owner will believe it is secure because the combination was 'changed.' Changing the combination on a defective lock launders a security problem into an apparently solved one. The correct sequence is diagnose and repair (or replace) the lock, verify single-combination operation across a full dialing cycle, then change the combination and re-verify.
2. The safe is open and the owner wants it done today. Outline the inspection and test sequence you would perform before and after any combination change.
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Before: (1) With the door open and the lock exposed where possible, inspect the wheel pack, drive cam, drive pin, fence, and boltwork for wear, looseness, or debris; check that the dial spins freely and that the spindle is secure with no slip. (2) Verify the relocker is intact and has not been defeated or taped - an auction safe is exactly where you find disabled relockers. (3) Dial the existing combination several times and confirm it opens reliably; then deliberately dial near-misses (including the 'one off' third number) and document whether they open. If a near-miss opens, the lock has a false gate or drive fault and must be corrected before any combination change.
After any repair or replacement: (4) Change the combination per the manufacturer's procedure, then (5) proof it - open on the new combination repeatedly (e.g., 10 clean cycles), and confirm that the old combination, the near-miss combinations, and a sampling of adjacent numbers all fail. (6) Record the work, the parts replaced, and the test results on the invoice, and give the owner a written statement of what was found and corrected. Do not hand back a safe you have not proofed against the specific failure it came in with.
3. How do you handle the owner's insistence that it 'has never been a problem'?
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You reframe the risk in terms she can act on, without overstating: a safe that opens on a near-miss is a safe whose effective combination space is far smaller than it appears, and the tag inside the door means anyone who has had the door open knows the combination. Both are real exposures regardless of history - 'it has never been a problem' describes the past, not the security of the container going forward.
Then you give her a clear choice with consequences: proceed with a proper inspection, repair if needed, combination change, and proof-test (recommended, and the only path on which you will warrant the work), or decline the combination change on an unverified lock and document that recommendation in writing. You do not silently do the quick job to please her, because the liability and the ethical exposure land on you. Getting her informed consent to the correct scope - in writing - is the professional resolution.