[Sager]

House wiring power is Black(hot) and White(Neutral-Common Ground). House does not have separate ground wire. Installing vanity Light with GFIC Outlet between Light and toggle Switch. Using Type NM-B 14/2 w/ground Romex 600V manufactured by Southwire. At Switch using black and white(white is tagged black). Switch and Outlet black connected to house black. Switch white (tagged black) connected to Light black. Outlet and Light white connected to house white. Connected Switch,Light and Outlet bare grounds together. (Note:Switch white (tagged black) and all grounds 'are not' connected to house wiring). Switch, Outlet, and Light are 'not' installed at this time. Light and Outlet white 'are' connected to house white. Using a tester that 'flashes red light and sounds audible beep' if senses current.
QUESTION-PROBLEM-CONFUSION:
Tester senses current at 'all' bare ground wires, and Switch white(tagged black) wire, not connected to any house wire. Outlet and Light White (connected to house white) 'do not' test as having current (as should be). The Switch black and Outlet black connected to house black 'do' test as having current (as should be). I do not understand why the bare ground wires and Switch white (tagged black) indicate there is current flowing when the wires are 'not' connected in any way. The circuit breaker 'does not' trip off to suggest any direct short between any wires. Your help and advice will be most appreciated.

[Tev]

That type of tester detects voltage, not current(amps).

I suspect that if the grounding wires were connected in the panel the breaker would trip. You very possibly have a connection between the hot and grounding wires but because there is no connection in the panel for the grounds it does not form the complete circuit that would allow the current flow necessary for the breaker to trip.

The reidentified white switch leg should show voltage when the switch is in the on position. Was it on or off when you checked it? As a side note, code requires the reidentified white in the cable be connected from switch to the circuit hot conductor and not from switch to light.

One thing you should never ever forget if you are going to be working with electricity. The neutral wire DOES carry current and is just as deadly as the hot wires.

[Missouri Bound]

... about these testers. They often pick up voltage on a wire that is not hot merely because it crosses or parallels another wire which is hot near the tester. I have found that if you are safely able to put your hand between the wire you are testing and the rest of the wire, you can almost always isolate it. (note the ALMOST ALWAYS) And ALWAYS check your tester first before assuming it works.

[hkstroud]

Switch white (tagged black) connected to Light black.

(Note:Switch white (tagged black) and all grounds 'are not' connected to house wiring).

I'm having difficulty following your wiring description. However, it sounds like you have an existing light controlled by a switch and are trying to install a GFI outlet (probably next to the switch) and install a vanity light or replace a vanity light. It also sounds like you have made some temporary connections to check your wiring before installing. The two statements quoted above appear to be in contradiction with each other.

What I suspect you have is the wiring shown below, where the white of the switch leg is being used to take power from the light box to the switch and the black is being used to take power back to the existing light fixture.

If I am correct that you are trying to install an outlet next to the switch, it can't be done unless you replace the existing cable between the switch and the light with 3 wire cable or run another cable between the switch and the light. You currently have no neutral at the switch. Both wires are hot.

Why not post back stating what you wish to do and what wires and connection you have in the light box and at the switch.