I am changing a o/h fan and light, I noticced a 31.7 volt reading with the light switch off, I know it's a short, wonder what's a easy way to find it, its old wiring from the 1920s, in a steel jacket most of the house is new romex wiring, thanks for any help

31.7 volts between what and what? Between hot and neutral, between hot and ground or between neutral and ground? When you measure voltage your are measuring the difference in voltage of two conductors.

What kind of switch, could the switch be a dimmer switch?

No, its a reg on and off switch, its more like a feed back then a short, so what could cause a feed back of about 31.7 volts ? Could a hot wire be touching something, maybe inside if the old jacket that would not kick the breaker... thanks

31.7 volts between what and what? Between hot and neutral, between hot and ground or between neutral and ground? When you measure voltage your are measuring the difference in voltage of two conductors.

What kind of switch, could the switch be a dimmer switch?
OK, I disconnected a run to some other outlets in the same and reconnected it...
Switch off is 0 from hot common, 0 from hot grd, about 17 volt reading at hot to grd and from grd to common... thanks

You don't have a common.

You have a hot. Hot is the term that is usually applied to the ungrounded conductor. The hot is usually, but not always some color other than white or green.
You nave a neutral. Neutral is the term usually applied to the grounded conductor. It is usually white.
You sometimes but not always have a ground. The ground is usually bare, green or sometimes the metallic sheathing of a cable.

The power comes in on the hot and goes out (back to its source) on the neutral. The neutral is also grounded at the panel.

The ground keeps the potential (voltage) of metallic parts the same as the physical ground. It is there for safety and not part of the circuity. The ground provides a path back to the source (the pole) through the moisture in the earth should you have a short between the hot and the metallic part.

At a switch you have a hot coming in and a hot going out to the fixture. The switch is not connected to the neutral. If you do a voltage check between the terminals of a switch in the off position, the meter will show a voltage. How much depends on what is connected at the appliance.

Let's say you have a switch on a light circuit. You do a voltage check between the terminals of the switch. The meter will show voltage. The circuit is from the hot through the filament of the light bulb to the neutral. The filament is a resistor therefore there will be a voltage drop. The meter shows that voltage drop.

Take the light bulb out and there will not be a complete circuit and the meter will not show voltage.

Thanks... trying that