Replacing switches on a 3-way switch that was wired up something like 100 years ago.

As the post says, my house has a standard light switch circuit with two switches using 3-way switches for each. It was wired correctly initially, because it did work as intended: if you flip either switch, the light will toggle. However, as I said, it was very very old, so the old switches eventually wore out and quit working entirely so I bought some new switches to replace them.

When I opened it up, I was greeted with this. It's a little hard to tell because my phone's flash washed it out a bit, but basically three wires with no labels at all. I don't have a multimeter. I was able to make an educated guess at which wire was the hot one, and after hooking it up the switches do work in that they turn the light on and off.

However, I got something mixed around somewhere. I read about circuits and even made a few test circuits in Minecraft to test out some scenarios but I just don't have the head for this and I'm guessing someone more familiar with this can probably fix my problem pretty trivially.

I made a chart of what happens when I flip the switches:

Switch A	Switch B	Bulb
on	off	off
on	on	off
off	off	on
off	on	off

What I think I did is turn an XOR gate into a simple AND, and I think to fix it I just need to swap the two non-hot wires on Switch A. However, I'm not at all confident in this and I'd rather ask someone for whom this is really simple than waste a bunch of time running to and from my basement to turn my power on and off as I experiment.

And I'll just stress again, everything in the underlying circuit is definitely correct because it worked with the old switches (until the old switches stopped switching). The only problem is in where I connected those wires to the new switches.

Thanks for any help!

Submitted April 08, 2016 at 04:49AM by shadow1515 http://ift.tt/1SDBsFh