Four years ago we purchased a home built on 1925. Much of the home has knob-and-tube wiring. Beautiful older home. Here is the problem. In the living room we have a nine foot ceiling (plaster and lathe). We want to install a ceiling fan. There exists an electrical box that was capped where there used to be a ceiling light. The previous owner said they could not get a light to operate. I called an electrician to ID the problem. He said it appears there is no ground. He suggested to cut out a section of plaster and lathe to look for broken ground. Did that and and found no break. Appears this is the only area not working in this circuit. Could wire be too old or brittle? What else should I look for? Any to test? Need advise.