I have an Ames non contact tester. When get a single beep/light next to a light switch not a constant beep or flash. What does this mean?
Switch – What does a single beep and one flash mean when using the Ames non contact tester
switch
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If all you have is one wire entering the switch, then the power for the switch might come from the light, and you just have a switched hot.
The white wire should be marked with tape to indicate it's not being used as a neutral.
Unfortunately, if this is the case, then you don't have a neutral available at this switch which is necessary for most of these automation switches. If there are other switches in this box it might be possible to re-route the power for this light, but I'd need to know more about where the power is coming from, what else is there, and how the light is connected in the ceiling box to help. Otherwise, the only way to this would be to run a new wire to the switch location -- either a new 14/3 from the light (so you have hot, neutral and switched hot), or a new power feed with 14/2 from the panel.
If you consider this simplified diagram, showing a light & switch, with the switch in the off position on the left, and in the on position on the right:
When the switch is OFF, its contacts are open - preventing current from flowing through the circuit to the light bulb.
When the switch is ON, its contacts are closed - allowing current to flow through the light bulb.
Your "voltage tester" is measuring voltage, not current.
When the switch is on the ON/closed position, your "voltage tester" measures 0V across the switch because that is exactly the case - a closed switch is a short-circuit and even though there may well be current flowing through it, there is no voltage across it.
If you were to put your "voltage tester" across the light bulb instead, you would find exactly the opposite case.
With the switch OFF/open there will be 0V across the light bulb and when the switch is ON/closed you will measure a voltage across the light bulb.
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Best Answer
Non contact tester will flash over nothing - tap your palm - flashes, slides across the dashboard - flashes, falls out of your shirt pocket, flashes as it hits the floor, and never works again.
It's important to remember that non contact voltage testers are simply not dead solid reliable testers.
There are lots of circumstances that will give you a false negative - it will fail to detect voltage present. There are not many circumstances where it will give you a false positive - usually it it lights up and stays lit it is seeing something.