question need help!!

thanks mario

Are you asking about electrical troubleshooting methods?
Or basic operation of the circuit?

Or is it that brain teaser question that goes like this:
You can not see the light and only get one chance to go back to see which one of three switches controls the light…

A circuit that has three switches for one light will have one 4-way switch and two 3-way switches. To properly check that they are wired right you have to go around and check each one more than once, you can have wiring errors where two of them work in certain positions but not if the other one is in the other position. Make sense? Nope, it can get confusing.

I wired several of those when I built my house, the hard part is when the power and load can not connect to the circuit where it would be simple.
Its simple when the power goes to one 3-way switch and the load is on the other and the 4-way is in the middle.

thanks bruce
i understand about three way switches at source and load and fourway in middle.but how would you test them if not working?what device would you use?what is the correct procedure?

First make sure the bulb is good and operate each switch to “feel” for any differences. Note that many 3-way switches require a higher force to switch than a regular and a 4-way even more, especially the Decora flat rocker types.

Two testing methods depending on the skill of the person, you can turn off the power and check for continuity through the switches, you need to know which terminal is the wiper or common and it is not always the one that it appears to be. A second person is very helpful when working with multiple switch locations too. The other method is with power on and only recommended for very qualified and experienced persons. As long as you see switching taking place it is not always necessary to know where each wire ends up to figure out which switch is bad. If the problem is not a switch but a bad splice somewhere it will take more effort and experience. Making a
drawing of the circuit really helps to sort it all out.

Due to the source and purpose of the question, the answer is probably something simple like, turn off power, verify no power is present, utilize ohm meter to isolate the defect by making simple measurements across the switch contacts to common and verify that the traveler conductors are good.


Since you can’t pull the cover on these switches your best bet is to simply flip the first switch on and see if it turns on the light…now go to the next switch and flip it and it should turn the light off…then go to the last one and flick it and the light should turn on again…

Now go back to the first one and try it again…should work the same way again…this is about all your can do during an inspection to make sure the travelers are right and so on…

thanks paul and bruce

this hepls i think this is what the instructor wanted to see on exam!!
i think what confused me was the wording of the question.


No problem my brother…it is a pleasure to assist anytime we can…:slight_smile:

His original question was not about inspecting, it was about an electrical course which I assumed to be troubleshooting and not inspecting…

“i understand about three way switches at source and load and fourway in middle.but how would you test them if not working?”

My Bad Bruce…lol…I thought the guy wanted to know how you would test them as a HI…otherwise you can’t pull the plates anyway so if they did not work AFTER you did the basic test I listed…then I would write it up and DEFER it…

Sorry…guess I didn’t help…lol…ok so I will rewrite that…

Glad Bruce could help ya…Thats what he is here for…thehehe;)