After Device Swap Now Half Circuit Dead: Decision Tree

Why this matters

When everything downstream of a just-swapped device goes dead, the break is almost always at that device. A receptacle or switch carries line-to-load through its terminals, so a feed-through wired to the wrong screws, a broken-tab split receptacle, a backstab that did not catch, or a line and load reversed kills everything past it while the swapped device itself may still work. Recognizing the half-dead pattern points you straight at the device you just installed instead of chasing the panel or the downstream boxes. It also catches the dangerous variant: a hot still present on a "dead" leg through a miswire.

Symptom presentation

• The swapped device works, but every outlet or fixture downstream of it is dead.
• A single receptacle's two halves behave differently after the swap, one half live and one dead, when the tab handling changed.
• A switch loop went dead for the fixtures it controls while the receptacles on the same circuit still work, or the reverse.
• A receptacle tester downstream reads no power, while the swapped device reads normal.

Quick checks

• Confirm where the dead zone starts: everything downstream of the swapped device, or a specific half of it.
• At the swapped device, identify which conductors are line (always hot) and which are load (feed-through to downstream). The line must land on the correct terminals to pass through.
• Check whether a receptacle's connecting tab was broken (split/half-hot wiring) when it should be intact, or left intact when it should be broken.
• Inspect backstab terminations: a conductor pushed into a backstab that did not fully seat carries the device but not the feed-through.
• Verify line and load were not reversed and that the neutral feed-through is also continuous.
• Count the conductors in the box. A box with two cables (one line, one load) is a feed-through device; landing the wrong pair on the brass screws breaks the chain. A single-cable box is an end-of-run device and cannot kill anything downstream, which redirects the search.
• Check whether the swapped device is a self-grounding or tab-style receptacle whose break-off fin was removed. A removed line-side jumper fin on a split-circuit device interrupts the feed-through even when both cables are landed.

Isolation tree

1. Define the dead zone. Everything past the device dead: the feed-through (line-to-load) at the device is broken. Half the device dead: the tab/split handling is the issue. A switched fixture dead: the switch loop landing is the issue.
2. Feed-through continuity. At the swapped receptacle, the downstream conductors must connect to the same hot and neutral as the line. If the line landed on one set of screws and the downstream on a broken-tab side or an unconnected screw, the hot or neutral does not pass through. Re-land so line and load share continuity.
3. Broken tab. On a receptacle, a broken hot tab splits the two halves. If the swap broke a tab that should be intact, one half and everything fed from it goes dead. Restore the tab or pigtail both halves from the line.
4. Backstab seating. Pull each backstabbed conductor lightly. One that backed out makes contact for the device face but not the downstream daisy chain, or drops out entirely. Move backstabs to the screw terminals and torque.
5. Line/load reversal and neutral. Confirm the hot feed and the neutral feed are both continuous to the downstream conductors. A reversed line/load or an open neutral feed-through leaves downstream devices dead or, worse, floating at hot potential through the load.
6. Switch loop. For a dead switched fixture, confirm the switch landed line and switched-hot correctly and did not interrupt the constant-hot feed-through to other devices.

Confirming diagnosis

• Broken feed-through: everything downstream dead; the line did not carry to the load conductors at the device.
• Broken tab / split error: half the receptacle and its dependents dead; the connecting tab handling is wrong.
• Unseated backstab: the device works but downstream is intermittent or dead; the backstab carries the face but not the chain.
• Line/load reversal or open neutral: downstream dead and possibly a hot present on the "dead" conductors; the feed-through path is wrong.
• Switch-loop error: the controlled fixture is dead while same-circuit receptacles work; the switch landing interrupted the wrong conductor.

Remediation

• Re-land the device so line and load conductors share continuous hot and neutral; pigtail rather than relying on a device's feed-through where the daisy chain is heavy.
• Restore or correctly handle the connecting tab for split versus standard wiring; pigtail both halves from the line when both must stay hot.
• Move backstabbed conductors to the screw terminals and torque to the device listing; backstabs are a common feed-through failure point.
• Correct any line/load reversal and confirm the neutral feed-through is continuous before re-energizing.
• For switch loops, land constant-hot and switched-hot correctly so the feed-through to other devices is not interrupted.

References

• NFPA 70 (NEC) Article 406, Receptacles, Cord Connectors, and Attachment Plugs (terminations, split-wired receptacles).
• NFPA 70 (NEC) Article 404, Switches (switch loop wiring).
• NFPA 70 (NEC) Article 110.14, Electrical Connections (terminal use, backstab considerations).
• NFPA 70 (NEC) Article 300, Wiring Methods (continuity of neutral, feed-through).
• NFPA 70E, Standard for Electrical Safety in the Workplace (verification of de-energized state).