I had the same problem In Darwin NT. The cats up there seemed to like spraying into the cars air vents and down the window. I tried covering my car in pepper and that worked for a while but the cats kept coming back so a more extreme measure was used.
I quickly constructed a 555 IC based oscillator driving a 2N3055 power transistor that in turn powered a surplus car ignition coil. The output of the coil was taken to a pair of thin TCW wires that zig zagged back and forth across my drive. The circuit was non lethal but acted like a cattle fence (on which I based the idea)
The cats very quickly learned to avoid my house and the electric fence could be removed and reinstated quickly whenever problems occurred :-)
If you think I was cruel...I love cats but not spraying....an Australian colleague at the station where I worked had a different approach....7 cats collected and taken to the tip in one weekend ..... he had shot them in his back yard
![Cry :'(](https://www.eevblog.com/forum/Smileys/default/cry.gif)
Apparently this is acceptable practice in Darwin as the Northern Territory is/was the 'Wild North' Frontier and Cats are considered non indigenous pests.
Aurora