Thank you for the replies and confirmation on the tester type.
1) Whenever checking for the presence of electrical voltage, it is always advisable to use a contact type of tester (either a 2 wire lead contact type or a Wiggy solenoid or an AC voltmeter tester).
2) Non-contact electrical testers check for the presence of electrical voltage based on inductance which is a form of magnetism. Any nearby metal and/or other electrical circuits can provide a false indication on the presence or lack of electrical voltage at the wires or cord. Thus the use of a non-contact voltage tester is never 100% accurate and should not be used as the sole test instrument to confirm voltage or lack of voltage as they are widely known in the industry to provide false indications.
Non-contact testers are commonly referred to as a "fools test instrument" by electricians since they can easily fool the end user into thinking that electrical voltage is either present or non present in a circuit. Electricians always use a 2 wire lead contact type of tester to confirm for voltages.
3) Yes, the cord insulation or nearby metal or another nearby electrical circuit can also have an impact and can provide a false indication of voltage present or not present. Non-contact voltage testers have their place in the electrical industry, but on a very limited basis and are typically only used under specific applications such as checking for a hot conductor in Knob & Tube wiring.
Since the pump is cord & plug connected to a receptacle, a contact type of tester could have easily confirmed that voltage is present directly at the receptacle.
4) The pump is working so it is evident that the circuit/receptacle is functioning properly.
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