just installed 2 new separate ceiling lights each with its own wall switch. The 2 wall switches sit beside each other. With analogue voltmeter I noted when both circuits are switched off there is 0 voltage across black/white wires on both circuit 1 and 2. But when circuit 1 is switched on and showing 120v, circuit 2 even though switched off, shows about 12 volts. Same occurs when circuit 2 is on and circuit 1 off.
I presume this is just phantom voltage and not too worry? or could it be something that needs repairing? House built in 1975, aluminum wires.
also, I installed new lights to replace the integrated LED units, one of which had broken down twice. The first time the LED unit lasted 4 yrs and started flashing and then went dim. Replaced with same unit from Lowes, it lasted 4 months and went dim. Still don't know why LED units failed, wondered if related to voltage issues. I replaced with standard fixtures.
Best Answer
This is called phantom voltage. When a cable is powering a device a field is generated, this field then induces a voltage on any wires in close proximity to the live wire. There is no problem here, this is related to how transformers work. I have seen phantom voltages close to the line voltage where there is a long run of multiple cables in parallel. The higher impedance the meter, the higher the voltage will be displayed. Their are low-Z or impedance meters that load the circuit enough to dampen the phantom voltages. But low-Z meters are not as sensitive for accurate measurements of electronic circuits so they are somewhat uncommon. I would not worry.