I have TWO 3-way switch in my hallway for light fixtures and I tried to replace one of the them to be a motion sensor switch. Both are working before the replacement, I can turn on and off with both way.

1st New motion sensor 3way switch will be nearby door and 2nd is located at the end of the hallway. floor plan

I find out the problem is if I install the motion sensor on the main door, when i open the main door, it will trigger the switch to turn on the light. Then, i switch off the light at the end of the hallway. When second guest come in, it won't trigger the sensor (i dont see the led light flashing on the sensor, unless you press the button manually to power on the sensor switch). when i switch ON the 3 way switch at the hall way. the sensor switch is flashing and it works.

This is the wiring on the sensor switch wiring on 3-way sensor switch

May i know how to wire it correctly. Thanks folks

  • What is the make and model of the motion sensor? Did you read the installation instructions?
    – Tester101
    Mar 24, 2015 at 19:09
  • Some sensors require that the other 3-way switch be wired differently, have you read the installation instructions to be sure that's not the case here?
    – Tester101
    Mar 25, 2015 at 10:11

2 Answers 2


After wrestling with 3way (i call them "two pole" but to each their own) switches I have learned that the only way out is patience and testing. Don't trust the wire colors. Unhook the switches from both sides (or just one switch if you are sure the other hasn't been altered since it was working), put wire nuts on the open wires, and power the circuit back on from the breaker/fuse. Get a multimeter and look for where the hot/neutral is and try to work out the other wires (which ones run to the fixture and which run to the other switch). If it's not obvious yet, check the fixture for voltage, you might find voltage there even with the switch off (second scenario below).

There are two types of 3 way switch wiring layouts. One has the power running from the panel to switch A, then 3 wires running to switch B (two alternating hot depending on switch position, plus one neutral) and finally 2 wires running from switch B to the fixture. The other option is similar but power runs to the fixture first and then to the switches to make/break the path.

You need to know which of these applies to you in order to know which terminals on your motion switch to use. From the look of the switch you have the black (live) wires hooked in but it's not clear if there is a neutral in there too (most motion switches need a neutral to work in a 3way setup). More details will be needed on your situation to provide a specific answer.

Edit, more info: Came across this good discussion (in case you haven't seen it): How do I wire a 3-way motion sensor?

The crux of the problem is that in a normal 3-way switch set up, neither switch really "knows" if the light is on or off, flipping it just reverses the state (for example you can have two switches up and the light is still off) so with a motion sensor you really need it to be in total control of the light, otherwise it might just turn it off after sensing motion when the light is already on per the other switch (not what you want). Most motion sensing switches have an accommodation for this but it is specific to the model.


In short, you don't really want to do this. The motion sensor is a simple two-position switch, and it can't be easily used in a circuit with three-way switches. You would end up violating the code requirement that there be two points of control of the light, one at each landing of the staircase, each able to turn the light on or off independently of the other.

  • Without knowing the make of the switch (it looks like it might be a 3 wire switch which suggests that it can be used in a 2-pole setup) how can you say it's not usable? He is asking how to make it work so that either the motion side can turn the light on/off, or the plain switch side can do so (as now the plain switch side overrides the motion side) Do you mean, in the case where the motion sensor turns off the light when the user doesn't want it to?
    – Jeff Meden
    Mar 24, 2015 at 19:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.