The fault isn't the timer — it's what the timer waits for

Sometimes nothing is broken — a step just times out because a confirmation never arrived. Read the timer's accumulated value against its preset, and the counter's count against reality, and the 'random fault' becomes a specific missing signal.

A faultline101 training module · the skill behind six hands-on scenarios

A step that times out is usually a confirmation that never arrived. Read the timer's accumulated value against its preset and a 'random fault' becomes a specific missing signal.

The idea

A timer fault is rarely the timer's fault. A step timer (TON) counts up while it waits for something — a sensor to confirm, a valve to stroke, a pressure to build — and faults when its accumulated value reaches the preset before that confirmation shows up. The fault is the missing confirmation, not the clock.

Read them online: the accumulated value versus the preset tells you exactly how long the step waited and whether it timed out. A retentive timer (RTO) that never gets reset accumulates across cycles and trips early. A counter that faults is either counting something real (over/under) or double-counting a bouncing input.

So when a machine 'randomly' faults, watch the timer accumulate live. If it climbs to preset every time because a device is slightly slow or a sensor never makes, the timer is honestly measuring a degrading part — chase the device, not the number.

Six faults you'll work in this module

You don't learn this by reading it — you learn it by doing it on six different faults, each drilling the same skill until it's instinct:

1. The step that times out. The timer honestly measured a confirmation that never came.
2. Runs, but the timing's wrong. The 'fault' was an edited setpoint, not a broken part.
3. The retentive timer that trips early. It trips early because yesterday's time is still on the clock.
4. The count that doesn't add up. The counter was faithfully counting a noisy, bouncing input.
5. The 'random' timeout. The timer caught a part on its way out.
6. Cold: which step stalled?. The accumulated value pointed straight at the stalled motion.

The mistakes it kills

• Raising a timer preset to make a fault 'go away' instead of finding the slow or missing confirmation
• Missing that a retentive timer never got reset, so it trips early each cycle
• Blaming a counter when a bouncing input is double-counting, or the count is genuinely off

Why it matters: Reading a timer against its preset turns a vague 'it keeps faulting' into 'the clamp-confirm sensor never made in time' — a specific part, not a mystery.

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