WiremanWireman · Smart switch won’t work (no neutral): troubleshooting for electricians · 2023 NEC ·
Smart switch won’t work (no neutral)
Smart switch won’t power up, flickers the LEDs, or drops offline. Usually a missing neutral or the wrong one.
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How it works
A smart switch has a radio and a processor that stay on all the time, so it needs constant power. A model with a neutral draws that from line to neutral. A no-neutral model trickles a small current through the lamp instead, which works with some loads and makes low-watt LEDs flicker or glow. Older homes often have switch loops: the cable at the switch carries only the hot down and the switched hot back up, with no neutral in the box. Newer work generally has to bring a neutral to switch locations, with some exceptions, so this is mostly an older-wiring problem. The neutral used has to be the one that belongs to the same circuit.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- What’s happening?
- The switch won’t power up at allTest: Look in the switch box
- A spliced bundle of white neutralsTest: Confirm the line and the neutralExpect: About 120 V line to neutral and line to ground, and the neutral is part of the same circuit as the line.
- 120 V to neutral and to groundLine and load swapped, or a failed switch
- 120 V to ground, about 0 V to neutralAn open neutral in the box
- The neutral is from a different circuitA neutral from another circuit
- One cable, white was on the old switchA switch loop with no neutral in the box
- Only conduit, no white conductorsA switch loop with no neutral in the box
- A spliced bundle of white neutralsTest: Confirm the line and the neutralExpect: About 120 V line to neutral and line to ground, and the neutral is part of the same circuit as the line.
- Lights flicker or glow when offIs the switch’s neutral lead connected to a neutral?
- No neutral connected (or a no-neutral model)A no-neutral switch powering itself through the lamp
- Yes, a neutral is connectedLoad or dimming compatibility
- Works, but drops off the network or resetsNetwork signal or firmware
- Tripped the breaker or died at installA miswire on the switch
- The switch won’t power up at allTest: Look in the switch box