Replacing an old 3 way switch with a new one
#1
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Replacing an old 3 way switch with a new one
I'm hoping for some guidance with a recent problem I'm having...
Recently a light switch broke in my kitchen. The light is switched from both ends of the room. My problem is that the switches are so old that they are not labeled, nor are the screws colored differently. The house was built in the late 50s so the wiring is all BX, and no ground wire. It's not clear in the pics, but the switch says "A-H&H" on the toggle and stamped on the chassis.
So here's what I've got going on: There is a black wire on top with a white wire, and a red on the bottom. When the lights are on (it's a ceiling fan), i have 64V A/C from the black to red, and also from black to white. With the lights off, 120V from black to red, and black to white. The white and red wires have continuity regardless of whether or not the light is on.
The goal is to replace this broken switch with a modern 3-way but I'm not 100% sure which wire is considered common (black screw) and which two wires go to the brass screws.
Recently a light switch broke in my kitchen. The light is switched from both ends of the room. My problem is that the switches are so old that they are not labeled, nor are the screws colored differently. The house was built in the late 50s so the wiring is all BX, and no ground wire. It's not clear in the pics, but the switch says "A-H&H" on the toggle and stamped on the chassis.
So here's what I've got going on: There is a black wire on top with a white wire, and a red on the bottom. When the lights are on (it's a ceiling fan), i have 64V A/C from the black to red, and also from black to white. With the lights off, 120V from black to red, and black to white. The white and red wires have continuity regardless of whether or not the light is on.
The goal is to replace this broken switch with a modern 3-way but I'm not 100% sure which wire is considered common (black screw) and which two wires go to the brass screws.
#4
If the wires are transposed the one switch may only work the light's when the one switch is in a certain position.
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Yeah that's exactly what's happening now. Just hooked it up.
Both switches have to be "up" now in order for the light to turn on. Before, the light would turn on when either switch was up. Is there a way to change this?
Both switches have to be "up" now in order for the light to turn on. Before, the light would turn on when either switch was up. Is there a way to change this?
#6
Now try using white as the common and black as a traveler.
Nothing will spark or short out if incorrect.
Nothing will spark or short out if incorrect.
#8
You may end up trying the third wire as common.
When finished..... note which two are travelers so that you know for the other end for when that switch needs replacement.
When finished..... note which two are travelers so that you know for the other end for when that switch needs replacement.
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Third time was the charm. The red wire was common. So now if anyone in the future has an AH&H 3-way light switch, and this thread comes up in a search, the bottom terminal is common.
Nice to see they wired SOMETHING in this house properly.
Nice to see they wired SOMETHING in this house properly.
#11
Thanks for letting us know the outcome.
The biggest problem is there no standard to where the C terminal is located on the switch.
Because of that very reason they started using a universal identifier.... a dark colored screw for common.
The biggest problem is there no standard to where the C terminal is located on the switch.
Because of that very reason they started using a universal identifier.... a dark colored screw for common.
#12
A 3-way switch doesn't have a top or bottom. They can be put in either end up. Was there by chance a letter "C" embossed on that end?
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Thank you for this thread! As someone who has absolutely no knowledge of things electrical, I decided to change out the old 1950's 3 way light switches in my house. I ran into the problem of them no longer functioning properly after I put in the new switch. Three wires, one red, one black, one yellow. I put them in the exact same location as they came off the old one, but no go. Finally figured out the yellow is the common and the black and red are the travelers. I'm guessing the switch was put in upside down as the common wire was top left, rather than on the bottom. Since there are no markings at all on the switch and all the screws are the same color, I also wonder how they managed to install them in the beginning!
So thanks to this thread, problem solved. I would never have figured it out other wise!
So thanks to this thread, problem solved. I would never have figured it out other wise!
#14
I'm guessing the switch was put in upside down
One common can easily be found by looking for where the power in hot is connected. Assuming both switches are identical then it also tells you which is common on the other switch. Even if the other switch is different you probably now know the color of the travelers on the other switch so you can guess the common location by elimination. Of coures K&T all bets off.