The old 1980 trailer I had, had rat chewed wires. The IDI RV had some chewed wires too. Both from before i got it.I did have a 2014 toyota car that I could not keep mice out of. Finally figured out they were getting in through the cabin air filter. They would chew a hole in it and fill the air box with acorns. Turn out, an insurance claim guy told me, that the insulation on the wiring in newer cars is made from processing soybeans which is why they like to chew it. I know this is absolutely no help but I do understand your frustration. I know they make some electronic deterants but I am not sure how well they workYou must be registered for see images attach
Those ultrasonic things don't work.
Don't Waste Money On Ultrasonic Pest Repellers, Grumpy Gardener Says
The Grumpy Gardener explains why he wouldn't waste his money on ultrasonic pest repellers. Stick with these old-school pest control methods instead.
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