That's funny - Here in the outskirts of Tucson, I had an AC go bad in my car when Janet and I were living near the foothills.
After a trip or two to the dealership, and some "repairs" that didn't work, we discovered packrats had been in the engine compartment nibbling on wires. Fixed the chewed wiring and everything was good.
There are several possible cures for this problem:
1. Kill all the packrats before they can damage your engine. The usual technique is to spread poison bait around in the engine compartment. It doesn't work.
2. Try to locate and remove all packrat middens in the vicinity. This is kind of like trying to kill all ants at a picnic.
3. Leave your hood up at night. The packrats don't find your engine compartment inviting, but battery thieves do (if your car stays outside).
4. Put a light that is always on (an LED) under the hood. Believe it or not, this actually works. You just hotwire it to the battery.
In Europe, they have Stoats. These little buggers (they look like small weasels) like to chew wires too. The cure there is to "stoat proof" the wiring. You wrap it in an armoured mesh jacket.
- Jack