I have a set of outside lights that no longer work. There is 120v from ground to the wire that exits the circuit breaker. At the light switch I get 120v from ground to the White wire, but I also get 15v from ground to the Black wire (with the switch in the off position). When the switch is on I get 120v from ground to the black wire. I assume my problem is with the black wire and that it's broken somewhere along it's path and I'm seeing 15vac because of that. Is this a good diagnoses?