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.