How did this light turn on?

[tonype]

Old home with a mixture of wire types (K&T, Type-NM, etc.).

A bedroom has a switch for a ceiling light, which activated properly (or so it seemed). It did not control any of the receptacles.

With the switch off, I started to test receptacles. When inserted into one, the ceiling light turned on. When the tester was removed, the light turned off. Anyone have insight into what is going on?

 

[LarryFine]

It sounds like that receptacle is in parallel with the switch, making it in series with the light.

 

[tonype]

It sounds like that receptacle is in parallel with the switch, making it in series with the light.

So, putting the tester in closed the circuit around the switch - thanks.

 

[LarryFine]

Is the tester a type (i.e., solenoid) that will pass enough current to energize the light (i.e., LED)?

Another possibility is the plugging and unplugging of the tester is wiggling a poor connection.

 

[tonype]

Is the tester a type (i.e., solenoid) that will pass enough current to energize the light (i.e., LED)?

Another possibility is the plugging and unplugging of the tester is wiggling a poor connection.

It is a Klein tester commonly used by home inspectors. The ceiling light was an LED

 

[masterinbama]

Loose neutral, possibly.

 

[jap]

I'm curious,

If you plug something into the receptacle and unscrew the light bulb in the ceiling fixture, does whatever you plug into the receptacle loose power?

JAP>

 

[tonype]

I'm curious,

If you plug something into the receptacle and unscrew the light bulb in the ceiling fixture, does whatever you plug into the receptacle loose power?

JAP>

I did not check for that.

 

[Sea Nile]

A bedroom has a switch for a ceiling light, which activated properly (or so it seemed). It did not control any of the receptacles.

So the light switch operated the light as you would expect. (It turned the light on and off) and at the same time you were testing the switch there was nothing plugged in to the receptacle.

And then with the light switch off, you plugged a tester into the receptacle and the light came on.

So since it's an older home, it probably has power fed to the fixture and a switch loop.

Is the power at the fixture fed from this receptacle?

My first step would be to take a closer look at the receptacle, if wiring looks good then look at the fixture.

Make sure the switch is toggling the hot and not the neutral.

And take everything I say with a grain of salt because I don't have a lot of experience

 

[Sea Nile]

So here is a thought. If the switch loop was mis-wired and you are swapping the neutral, that means the fixture is always hot and just waiting for a connection to neutral or ground to complete the circuit.

If the tester is a push button type, does it short ground and neutral when you push the button? (I honestly don't know). But if so, can this connection provide the path back that the fixture was needed, assuming the fixture was always hot, via objectionable current on the bonded portion?

 

[jap]

One of many possibilities,,,,



JAP>