Re: Knob & Tube 3Way Switch
There are a few things you need to consider when dealing with knob & tube wiring. The first thing is they can be very brittle and the insulation can start falling off exposing bare conductors. The second thing to consider is how 3-way switches were once wired. At one time when houses were wired with knob & tube, they would feed the 3-way switches with a hot and neutral. They would then send a single conductor from the point screw of the switches to the light(s). The switched would either send up a neutral signal or a hot signal depending on the position of the switch. This is often called lazy susan switching. If the lazy susan wiring gets changed around on the 3-way switches you end up with a short circuit (hot to neutral short). Since it does not sound like you have this issue you probably don't have lazy susan wiring.
Typical 3-way wiring will have a feed (hot wire) at one point screw of a 3-way switch (black screw) and the travelers would be on the two travelers screws (brass screws). The other point wire on the other 3-way switch will go to the light(s).
If the light does not work at one switch the issue you are probably having is you have switched a traveler and a point wire.
To solve this issue you will need a volt meter.
Pull out both switches and find out what wire is the feed (hot wire). This wire will go onto the point wire of the 3-way switch. Then you will connect them to the two wire to the travelers.
Use your volt meter to identify the travelers. These wires will be hot one at a time as switch one is flipped up and down. Once you have identified theses two wires they will be connected to the travelers. The other wire will be connected to the point screw of the switch.
This should resolve you’re wiring issue.
Since a picture is worth a thousand words I have attached a link to a diagram.