Red Hot leg of 14/3 cable disconnected at panel but still picking current somewhere from the other leg. Circuit breaker does not trip. Everything works ok on the good leg. How do I find the fault?
Both a non contact tester and a voltmeter will show voltage on a disconnected wire that is running parallel to a hot wire. Using A load like a light bulb put on the red wire to neutral will take the voltage closer to 0. If there truly is a short from another hot wire to the red the bulb will light. If the bulb lights the short could be in any junction box or at a staple holding the wire in place, the last possibility is a nail or screw was driven through the cable. There is a tool that can scan through walls that some electricians have that can pinpoint an open or short through the walls. I would double check and verify the voltage with a load because most times it is just induced voltage from running with another wire.
A disconnected wire will pick up voltage inductively, like an antenna.
If you've ever built one of those crystal AM radios out of thin wire and a toilet paper roll, you know inductive energy can drive tiny loads like a very sensitive earpiece. Or a modern digital voltmeter.
But it isn't good for much more. Connect any sort of load to it, even a simple night light, and that stray voltage will quickly disappear.