Does your county have a vector control district? If so, call them.

Not only do moth balls not work for controlling rats, it is illegal to use them in that manner. The health hazards posed by naphthalene are too numerous to mention although the linked article does a good job of that.
A bait, that is more appealing to them then the insulation of the wires, with an anticoagulant as the main ingredient, as well as traps.

Here is a link that might be useful: About Moth Balls

greyfox39, pre-baiting was a technique that was started in the 1950's.
This has been successful each time.
Obtain a 'snap trap' and super glue it to an "out of the way" place (inside the trunk?) and place a suitable bait (bacon or cheese)on it but do not set the trap.
You want the animal to feed on the bait. Be patient.
Rats and mice are very suspicious but extremely curious.
Replace the bait each night ... and one morning it will be missing. Replace it as often as you want to.
Then one night bait the trap and set it.
At some time during the night that rodent will leave his hiding place and run blindly to the bait ... and the last thought that will pass through its little brain will be "What the ????"