Ungrounded 3-way Switch - Replacing

[bczygan]

In the garage, at the garage door, I have a 3-way switch that is broken. The toggle is smashed and needs jiggling to make it stay turned on and off.

So I'm replacing it.

A couple of questions.

It I turn the other 3 way so the garage ceiling light goes off, does it cut power to this switch?

This switch has 4 brass terminals, and no ground, since the entire house has no ground system.

This original switch had one wire on the upper left and a wire on each of the right hand terminals.

Do I use a new 3 way switch and hook it up the same way and just leave the ground unattached?

Bill

 

[dogdog]

I think it is easier for you to understand if you just google the 3-way switch diagram.... the one that matters is the black screw ........

maybe you have a 4-way switch instead?

 

[alfredeneuman]

If you turn the other 3 way off the switch your working on would definitely still have power.


There are 3 wires on a 3 way switch: 1 common wire that can be used either for the incoming power or the wiring to the light, and 2 travelers that transfer the power to the other wire depending on whether it's up or down.

Better identify the breaker, and shut it off.

 

[bczygan]

I think it is easier for you to understand if you just google the 3-way switch diagram.... the one that matters is the black screw ........

maybe you have a 4-way switch instead?

The wires connect like the ones on the left, as far as location of wire connections. but the wire colors are all the same, and how they connect to the original switch is unknown. This is obviously the switch at the end of the line. This switch has 4 brass colored terminals and screws, and no ground screw.

Do I just buy a new 3 way and connect it up the same and just leave the ground off? It's a metal box and cover BTW.

Bill

 

[justsam]

Are you sure there are only two locations that the light can be turned on/off? Sounds like the original switch was really a four way switch, but only being used as 3 way.

I would replace with a regular 3 way, ground on the new switch will not be used. The common terminal will have either the light itself, or 120v at all times.

 

[Mustang51js]

Look at the old switch and look at the new switch, there will be a screw that is different color than the other two screws,that is your point, as long as you take the wire off the odd color screw and put it on the odd color screw of new switch it doesn't matter what screw you put the other two wires on as long as it's not the green screw. If you have a ground wire then that goes on the green screw

 

[Mustang51js]

Or if you look in the box and you have a 3 wire and a 2 wire, the black from the two wire will be your point and the black and red from 3 wire will be your travelers with the neutrals wire nutted together. Take a pic of old switch if you can

 

[nehog]

I suspect that someone substituted a four way switch for a three way.

 

[bczygan]

Here is a photo of the box and both sides of the switch.

This is circa 1941.

 

[justsam]

The wiring looks pretty fragile, so I would not recommend trying different combinations until you get it, unless you do it with some clip leads to the old wiring.

Can you determine, with a voltmeter, if one of those three wires is hot all the time, regardless of the other three way switch position? That will be a good starting point. I am going to assume the conduit is ground so measure from each of the three wires, to the metal box.

Also what type of light is this turning off and on, is it a regular incandescent, CFL, or?

 

[Mustang51js]

Well you only have three options,I would try the wire on top first on the black screw and the two wires on bottom onto the brass screws. You could put wires on screws but not tighten down just to test to make sure it works right. And that old switch is a 4 way used as a 3 way. You have a 33.3% chance of getting it right the first time lol.

 

[bczygan]

OK guys.......why do I need to do any testing at all.

Each of the three wires is in the same position that they were before.

Can't I just hook them up as before?

Does it matter the color of the terminals?

Remember, the old switch had 4 brass terminals.

It's an LED bulb in a porcelain ceiling fixture, if that matters. I could change it out for an incandescent if the wrong connection could blow it.

Bill

 

[Zeke]

The wrong connection won't blow the lamp, it will trip the breaker. At least you'll know which breaker it is.

Here's what I'd do: using a meter test the 3 possible combinations at the box. Note which 2 light the meter. Go to the other switch and flip it, rinse repeat. By doing this you should discover the common. As mentioned, the other two can be hooked up to the traveler lugs which are identified.

 

[bczygan]

The wrong connection won't blow the lamp, it will trip the breaker. At least you'll know which breaker it is.

Here's what I'd do: using a meter test the 3 possible combinations at the box. Note which 2 light the meter. Go to the other switch and flip it, rinse repeat. By doing this you should discover the common. As mentioned, the other two can be hooked up to the traveler lugs which are identified.

Thank you Zeke!

I'll try that.

 

[Mustang51js]

OK guys.......why do I need to do any testing at all.

Each of the three wires is in the same position that they were before.

Can't I just hook them up as before?

Does it matter the color of the terminals?

Remember, the old switch had 4 brass terminals.

It's an LED bulb in a porcelain ceiling fixture, if that matters. I could change it out for an incandescent if the wrong connection could blow it.

Bill

Only reason you need to test is because all three way switches aren't set up the same,so you may have to do trial and error. With those three wires you have you won't trip the breaker since they can all be hot wires,if you connect the ground to one of the screws that are for the hots then you will trip the breaker. I fix three ways all the time and for the same reason you are thinking with your switches, people take a switch out and put wires the same way back but don't realize the point(black screw or copper color) are not in the same position as old switch, so then you turn off one switch and then it only works from one direction.

 

[kenfath]

Did your new swiitch come with a wiring diagram?

 

[justsam]

Just determine which screw is COMMON on the new switch, probably a BLACK screw.

Try each of the three wires on that screw one at a time.

The other two wires can go on either of the remaining screws.

Change combinations until you get it to work properly at each switch location.