We had a pickup truck we kept at a deer lease. Mice would chew the wires.
We found out that disconnecting the battery worked.
They stopped chewing the wires when de-engergized. No idea why or if it would work for anyone else but it worked for us.
I realize its not practical on a daily driver though...
Mouse traps baited with peanut butter will help reduce the population. But I have no problem killing varmits.
