Is This Failure Your Fault or Normal Wear: A Decision Tree

Why this matters

When something you worked on fails, one question decides whether you owe a free repair: did your workmanship cause it, or did the thing simply wear out on its normal schedule. Answer "my fault" and it is a warranty event you fund. Answer "normal wear" and it is a paid repair the customer owns. Get it backward in the generous direction and you give away money on failures that were never yours. Get it backward the other way and you deny a claim you caused, and the customer knows. This tree is the attribution call, aimed squarely at the warranty-liability question, not at whether the rest of the unit will follow.

Safety first, if the failure is live

If the failed item is actively unsafe right now (leaking gas, arcing, water into live electrical, anything that can hurt someone), stop and make it safe before you attribute anything. Attribution is a paperwork question; a live hazard is not. Handle the danger first (see the smell-of-gas-or-burning tree), then come back to whose fault it is.

Start here: time in service versus expected life

Pull the completion date of your work and the realistic service life of the part, and compare.

• If the part failed early in its expected life: normal wear is unlikely, so lean toward workmanship, a defect, or a condition problem. Healthy parts do not wear out early without a reason, and if that reason is how you installed or applied it, the failure is yours.
• If the part reached the far end of its expected life: normal wear is the strong default. A part that ran its design life and quit is not a workmanship failure, and you do not owe it.
• If it is mid-life: time alone does not decide it. Read the part.

Read the failed part: wear looks different from a miss

The part carries the evidence. Two signatures separate normal wear from your workmanship.

• Normal-wear signatures: smooth, even erosion or thinning, polished contact faces, dried and cracked rubber, accumulated scale, bearings with genuine mileage, a gradual loss of capacity. Everything looks uniformly tired. This is time doing its job.
• Workmanship signatures: the fault sits exactly where your hands were. A connection you made that loosened or overheated, a fitting you sealed that leaks, a fastener you set that backed out, a part you positioned that chafed or was strained. Localized failure at the point of your work, on a part that is otherwise not worn out, points back at the install.

Uniform tiredness is wear. A fresh fault at your work point is a miss.

Check for premature wear: the trap in the middle

The hard cases are parts that show wear but wore out too soon. Premature wear is often workmanship wearing a disguise, because the install condition is what accelerated it.

• Was the part oversized, undersized, misaligned, over-torqued, run dry, starved for flow or air, or fed the wrong supply because of how the job was set up.
• If a condition you created shortened the part's life, the "wear" is downstream of your workmanship, and the honest call leans toward yours even though the part looks worn.
• If the premature wear traces to the customer's use, a skipped maintenance interval, or an outside event after you left, it is not your workmanship, even though it failed early.

Premature wear is the branch where careful techs separate themselves from lazy ones. Do not let "it looks worn" end the inquiry when the part had no business wearing out yet.

Calling it

• If the fault is at your work point, or a condition you created caused premature wear: this is your workmanship. Honor it as a warranty repair without a fight.
• If the part ran its expected life and shows uniform wear: this is normal wear. Not covered. Explain it plainly and quote the paid repair or the replace conversation.
• If it is genuinely mixed, or the evidence is ambiguous: treat it as a goodwill judgment, not a clean denial. Route it to whoever holds goodwill authority and decide the relationship value on purpose (see the out-of-warranty exception tree).

The recap

1. Make it safe first if the failure is live.
2. Compare time in service to expected life.
3. Read the part: uniform wear versus a fault at your work point.
4. Test for premature wear caused by an install condition you created.
5. Call it: your warranty, normal wear, or a documented goodwill gray area.

The honest attribution is the one that holds up when the customer asks you to explain it to their face. If you would be uncomfortable saying "that is just normal wear" out loud while looking at a fault sitting right where you worked, it is not normal wear.

References

• Reliability engineering wear-out and infant-mortality failure models (bathtub curve)
• Manufacturer documentation on expected service life (generic, by component type)
• See related: Age-Related vs Defect-Related Failure (decision tree); Separating a Workmanship Defect From a Part Failure