dtheobald

I am replacing some of my old light switches. They are like decora switches, but the button is the full size of the switch plate. They are horrible. I boutgh new switches and covers to do the job a little at a time...as my house has arouns 25 of these horrible switches.

Anyway...I turned the power off at the breaker box and removed the switch plates and pulled out the old switch on a double switch box. One of the switches only had 2 lines going to it...the other had 3 lines going to it. This confused me a bit, so to be safe I thought I would try to ask around and do some research.

THese are not on dimmer and to the best of my knowledge, they are not 3 way switches.

Any idea why one switch has 3 wires, the other only 2???

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Devin

joecaption

If there's one black screw, two gold screws, and a green for ground it's a 3 way switch.
As you remove the wires do them one at a time and connect it to the new switch so you do reverse one of the wires.
No idea why there would be three wires if it's not a three way. Sometimes it goes to a wall outlet not a light.

dtheobald

That could be it, it does control a Ballast for 3 flourescent bulbs, but they both do. maybe the ballasts it powers are plugged in somewhere...THe house does have 'lamp switches' as I call them. I really dont think it is a three way switch...if it is, I cant find the other switch?

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Devin

nealtw

Does each wire have it's own screw?

JoeD

This has nothing to do with the ballasts. If the switch had three screws it is a three way switch. There is another switch that also controls this same light.
'Please describe the switch and what it controls. Is there another switch that also controls the same thing?

joecaption

Three way swithes have 4 screws not 3.
Three for the hots and one for ground.

JoeD

Switches in Canada don't all have the grounds. So I guess I should have three screws + a ground if present.

joecaption

Old switches anyplace may not have grounds but any new ones will and it's code that they do.

East_Texas

The switch with two wires going to it is pretty much standard in that it controls the power to one light or outlet, or perhaps two outlets that are wired in parallel for instance lamps on each end of the sofa. The one with three wires could either be for a three way circuit or again just a switch controlling two outlets like maybe on different walls. It the wires are all on separate screws then it is most definitely for a three way circuit, if two of the wires are on one screw then it is just a switch controlling multiple outlets. The most important thing is to replace the switches with switches identical to the ones you remove. If the switches are old enough they may not have the green screw for ground, but other wise they should have the exact same amount of screws and replacing the wires is as simple as taking one wire at a time off and attaching it to the new switch until all wires are moved.

joecaption

And there should neve be two wires under one screw. The incoming wires needs a pig tail attacted and only one wire under the screw. The screws are not long enough to be tightened properly with two screws and may strip out if you try it.