Q&A / 

Wiring 3 and 4 Way Switches

DEAR TIM: I have two interior hallway lights that are controlled by 3 separate electrical switches. My husband tried to install new decorative switches and now the lights come on only part of the time. What in the world do you think he did wrong? I need an aspirin! R.L.

DEAR R. L.: In all fairness, he may have done nothing wrong. You possibly have a defective switch. However, the smart money is on your husband. Sounds like another weekend warrior who was not prepared for battle.

Your problem is a fairly common one. It involves what are known as 3 way and 4 way electrical switches. These simple devices create more problems than they deserve. Your headache will vanish with a little effort on your part. Let's take a quick electrical switch 101 course.

How to Wire a 3-Way Switch Video

Okay, look at this 3 way switch. Note the different colored screws.  The top one is brass and the bottom one is black.  The other two screws you can't see are brass and green. The continuous hot wire and/or the wire that goes to the light connect to the black screw.  The ground wire connects to the green screw and the travelers connect to the two brass screws.

Okay, look at this 3 way switch. Note the different colored screws. The top one is brass and the bottom one is black. The other two screws you can't see are brass and green. The continuous hot wire and/or the wire that goes to the light connect to the black screw. The ground wire connects to the green screw and the travelers connect to the two brass screws.

Three way switches are used to control a light or other electrical device from two different points. Four way switches are used in conjunction with two 3 way switches to control devices from 3 or more points.

The placement of the switches is critical. The 4 way switches must be in between the 3 way switches. In other words, the power from your circuit panel must first enter the 3 way switch before it goes to the 4 way switch. From that 4 way switch it then travels to an additional 4 way switch or, in your case, to the final 3 way switch. The path that the electricity follows as it passes between the switches is not unlike a railroad switching yard.

Three way and 4 way switches are easy to distinguish. A 3 way switch has 3 terminals (not counting the green grounding terminal) or locations where wires attach. A 4 way switch will have 4 terminals. In almost all instances the 3 way switches will have one of the three screws painted or tinted a dark color or black. This is important! The 4 way screws are almost always a standard brass in color.

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