Our overhead kitchen lights (florescent fixture) stopped working yesterday. The fixture is controlled by a "3-way switch" setup (separate switches for each entrance into the kitchen). First, I turned off the power to the kitchen light circuit and individually tested the switches for continuity; both seem to work properly. So then I tested the voltage coming into the light fixture (with the ballast disconnected on the hot end). With the switches set such that the light should be on, I read 35V. Huh? So I switched one of the switches off. Power from the ceiling (just a hot and neutral with no ground) was still at 35V. No matter the 4 possible combinations of the switches, the light fixture was always being fed 35V (which I expect isn't enough voltage to fire up the ballast). I then tested between the hot and neutral at one of the two switches. It read 71V. Huh??? again!
This is a strictly residential, single-family house with standard 200A service - no multi-phase supply nonsense. It is a 70 year old house, so some of the wiring (the original wiring) is somewhat nasty. With however my meter is calibrated, wall sockets measure at 125V (at least in the expected range); the bathroom lighting shares the breaker circuit with the kitchen lighting, and a socket in the bathroom light fixture also measures at 125V.
What could be going on to explain this (I mean specifically, not just "bad old wiring")?