Simple Electrical Switch Question

OPTIMO

Learn me some electrical. I'm replacing a pair of 1960-era light switches with a switch that has 4 connections.

On the back the top two (A, B) read: strip gauge

The bottom left is the ground (not pictured).

The bottom right (C) says Common.

Out of the wall I have a jumbled mess. After taking a multimeter to them I realize I only have one HOT (which is why it was probably spliced off and used at both switches) and a ************ ton of grounds.

A & B always complete a circuit.
B & C complete a circuit when the switch is OFF.
B & C fail to complete a circuit when the switch is ON.

I've also figured out that the downstairs bathroom lights are wired into this mess somehow (found out after playing with combinations). Is there an easy way to trace a wire and fight out if it's in another location? Like put a clip on one end and a toner on the other or some ************?

UGH.

So is A the wire to the light fixture?
B the wire to power?
C a wire to a local ground?

I'm confused and could use a little help.

frenchelectrican

Woah , stop a min please

for the Three way switches you should see a dark coloured screw which it called common and other two is travallers.

right now dont worry about the ground wire [ bare copper wire ] leave that aside for a min just contracted on the main wires for now.

if you are replaceing both 3 way switches at the same time.

here what you have to do here i know it will tick you off a little but bear with me there is about 9 diffrent way to get the 3 ways working right.

you have to tell me what colours the wires you got on the switchbox right there at both loacations and the numbers of cables go in the box [ this part you can tell by the groups of wire[s] at each spots normally most percentage it will be black and white but there are some wire it will have black and white and red as well.


right now the main point is find the hot lead at first which you did that is the common lead keep in your mind the common is a hot wire or a wire wil go to the light fixure

the A is common but B and C is trallver so check the other switch as well and watch the wire colour if the wire colour not match up please post it back here

that what i will suggest that make sure both switches are at the same pattern of connectons this is one way you do it right

Merci, Marc

note that there are few other guys will help you here also so bear with us they will pitch in too

HouseHelper

Sounds like you are trying to install a 3-way switch where two single pole switches used to be, That won't work.

How many wires were connected to the old switches? Are there multiple switches that control these lights? What color are the wires in your jumbled mess?

fw2007

A & B always complete a circuit.
B & C complete a circuit when the switch is OFF.
B & C fail to complete a circuit when the switch is ON.

Are you sure you've got that right?
I'm betting that A&C should complete a circuit when the switch is ON.
A&B should NEVER complete a circuit if C is the common.

It appears that someone used the switch box as a junction for other circuits.
That was common with knob and tube wiring.

Note that some of those "ground" wires may actually be the A&B wires to the other switch. They may appear to be at ground potential if the lamp is not on.

Here is a diagram of how a 3-way switch circuit works:

J. V.

This was discussed for two days a couple of days ago. Go back through the threads for last week. You will find all the answers you seek.

Learn me some electrical?

OPTIMO

Thanks for the help everyone. A lot easier with the right switches.