[nudephil (OP)]

An interesting conundrum from listener James:

I bought a car. I'm naïve regarding vehicles and I didn't look under the bonnet. It now is throwing up wiring issues after only 3 weeks. A rat has clearly eaten at a few parts, particularly the foam that's there for sound proofing.

I am convinced it was chewed prior to me buying the car. Is there any way to "carbon date" the rat bites on the foam?

[Bored chemist]

Take a picture.
Wait a week.
Take another picture.
If the pictures are essentially the same there's nothing eating your car now, so it must have happened earlier.

Or you can look for rat droppings with plastic foam in at the previous owner's garage.

[Hayseed]

Did it run alright a day or two after you bought it?  Have you rodents in your area?  Any debris on floor under car at your place?

[set fair]

It's hard to imagine how a rat biting through a wire would cause an electrical problem three weks later.

[Bored chemist]

It's easy to imagine a rat bite weakening a cable so that it fails a few weeks later.
It's quite hard to imagine that the OP hasn't found some sort of resolution to this issue in the intervening months since he posted about it.

[Origin]

I had a rat that decided it would be a great idea to chew the wires on my car.  I took it to the dealer and the fixed it for a bunch of money.  My wife suggested I see if our insurance would cover it.  I thought that was a silly idea but I called anyway.  Yep, they covered it.  Go figure.