WiremanWireman · 4-way switch problems: troubleshooting for electricians · 2023 NEC ·
4-way switch problems
Three or more switches for one light. Keep each traveler pair on its own pair of screws.
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How it works
A 4-way switch sits between two 3-way switches and only handles travelers. It has four screws in two pairs: one pair takes the two travelers from one 3-way, the other pair takes the two travelers going on toward the other 3-way. In one position it passes them straight through; in the other it crosses them. Each 4-way you add goes in series on the travelers. The usual mistake is putting the wires from one side across both pairs instead of on the same pair.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- What happens?
- With the 4-way one way it works; the other way it’s always offTest: Find each cable’s traveler pair
- A pair was split across both sidesA traveler pair split across the 4-way
- Each pair was on its own pair of screwsA failed 4-way switch
- The 4-way does nothing; the 3-ways workTest: Bench-test the 4-way and find its pairsExpect: In each position, each screw beeps to exactly one screw of the other pair, and the partner changes when you flip it.
- Fails: a screw never connects, or nothing changesA failed 4-way switch
- Tests goodTest: Find each cable’s traveler pair
- A pair was split across both sidesA traveler pair split across the 4-way
- Each pair was on its own pair of screwsA failed 4-way switch
- Works only in some combinationsTest: Take the 4-way out of the picture
- Yes, both 3-ways work nowTest: Bench-test the 4-way and find its pairsExpect: In each position, each screw beeps to exactly one screw of the other pair, and the partner changes when you flip it.
- Fails: a screw never connects, or nothing changesA failed 4-way switch
- Tests goodTest: Find each cable’s traveler pair
- A pair was split across both sidesA traveler pair split across the 4-way
- Each pair was on its own pair of screwsA failed 4-way switch
- No, still wrongA 3-way is miswired
- Yes, both 3-ways work nowTest: Bench-test the 4-way and find its pairsExpect: In each position, each screw beeps to exactly one screw of the other pair, and the partner changes when you flip it.
- The breaker trips when a switch is flippedA neutral or second hot is on a traveler
- Never works from any switchNo power, or a fault before the switches
- With the 4-way one way it works; the other way it’s always offTest: Find each cable’s traveler pair