The fundamental difference between three-wire and four-wire switches:
A motion-sensor switch acts like a smart light controller. A three-wire switch is the basic version (live wire/neutral wire/load wire), while a four-wire switch adds a signal wire (live wire/neutral wire/load wire/signal wire). A four-wire switch can control multiple lights simultaneously; for example, two adjacent lights might turn on when a cabinet door is opened, while a three-wire switch can only control a single light. The wire colors are typically: red for live wire, blue for neutral wire, yellow for load wire, and black or white for the signal wire in a four-wire switch.
Wiring Steps (Illustrated Guide)
Three-Wire Wiring: After disconnecting the power, connect the switch's live wire (red) to the power supply's live wire, the neutral wire (blue) to the power supply's neutral wire, and the load wire (yellow) to the light fixture's live wire.
Four-Wire Wiring: The first three steps are the same as the three-wire wiring. The additional signal wire (black/white) needs to be connected in series to the other switch's signal terminal.
Power-On Test: Keep the light fixture disconnected. Use a test pen to confirm the switch output is normal before connecting the light fixture.
Error Prevention Tips and Scenarios
In humid kitchen environments, it is recommended to wrap the wiring joints with waterproof adhesive. The signal wire length should not exceed 3 meters to avoid attenuation. If the light remains constantly on, check if the load wire is incorrectly connected to the neutral wire; if the response is sluggish, the signal wire's positive and negative terminals may be reversed. Four-wire wiring is preferred for high-frequency use scenarios such as bathrooms; three-wire wiring is more economical for ordinary storage cabinets.
