Yard Light has Volts but no light
There should be 120 volts AC between the red and black wire.  Or sometimes, 12 volts DC.  If there is not, there is no power there. 

Electrical power works in loops.  There need to be 2 wires involved or nothing happens.  The way we do electricity in the US, the white wire is one of those two wires, but it is kept as close to earth ground as possible, so it is called neutral. 

One way power can fail is for the white (neutral) wire to become disconnected or damaged.   This breaks the loop, obviously.  And since it is not connected, it will pick up stray voltage by induction.  In which case you can see a weak phantom voltage on the neutral.   If a non-contact tester shows voltage on both, perhaps that has happened.