I'm replacing a light with a fan, so I replaced the box for more support. This circuit seems to go all over the place, involving 6 light switches and 3 rooms. There were (2) 14-2 wires and (1) 14-3 wire coming in to the light box (although there are no 3-way switches on the circuit). When rewiring, I started questioning myself so I got out my meter. I'm getting weird voltages across various hot (black) wires where I expected none. In one case, I get 97 volts across my main hot red lead coming from the light switch (when measured across the main black coming from the circuit breaker) when the switch is OFF. When I turn the switch ON, i get 120v. On two other hot leads going to other switches I get 120v when measuring to the main black line. If I tie all the blacks together (except for my hot red coming from the switch for that light, and tie all the whites together, everything seems to work and be happy at 120v across the black and white bundle, and I get 120v across the red hot and white bundle, so my fan/light will work fine. My problem is that I'm confused, and I don't want to cover up a potential fire hazzard just because "it works".
The only thing that would make some logical sense to me is if some device or devices on the circuit were in the 'ON' position, then would that allow voltage to bleed from the white side of a the circuit to the black side? That may be totally wrong, but it seems like a possibility to my brain... I can't justify any other reason why I'd be able to measure voltage across two 'hot' wires.
i would recomend you sort out the wires by finding where they are coming from. do not just tie like colors together, sometimes people wire whites as switched hot and don't re-color code the wires. once you sort them out write back with questions.