Capstone: Diagnosing a Dead Branch Circuit (Integrated)
This ties Module 4 together. A homeowner reports several bedroom receptacles are dead, but the breaker is NOT tripped. Here's the professional diagnostic logic.
The method
- Work safe first. Verify your tester (live-dead-live) and wear appropriate PPE before you probe anything.
- Read the symptom. Dead circuit but breaker not tripped → this is an open, not a short (a short would trip the breaker instantly).
- Check for voltage at the first dead receptacle — voltmeter in parallel across the slots.
- 120 V present but the plugged-in device won't run → the fault is in the device/cord.
- 0 V present → the open is upstream (feed side) of that point.
- Usual suspect: a loose or failed connection — a backstabbed device or loose wire nut is the classic intermittent/dead-circuit cause.
- Find the open: de-energize and use a continuity/ohmmeter test, working section by section.
- If it trips immediately on reset instead: that's a short circuit or ground fault, not an open — different hunt.
- AFCI tripping repeatedly (bedrooms are AFCI-protected): suspect a real arcing fault or a wiring error (shared/miswired neutral).
- Verify the repair: re-energize, confirm correct voltage and operation, and re-test any GFCI/AFCI.