A fried converter, has anyone had this covered by insurance?

I am not sure I agree with their assessment in that there wasn't a breakdown or malfunction of your electrical system, it was a result of plugging into a faulty electrical system. Not the first time insurance an insurance company balked at a claim. That said, it really depends on where you plugged into. Seems to me, if the electrical source you plugged into was faulty, it would be the responsibility of the owner of that electrical system. Was this at a campground? 

ya extended mechanical insurance is a pain to get anything done.  I didn't use mine at all and got 60% of the cost back as the repairs I had to make were less than the deductable if I did the work myself.  the only times I have gotten electric stuff fixed was under the original manufactures warenty for an auto changover switch.  

I agree with way2roll, if you know it was a faulty power asource that should be under the liability of the park owner to cover, but it is also your responcibility to know that stuff like this could happen and have a surge protector that shows if the power source is good or not, they are cheep insurance.  

The other side of the coin is, he did not provide us with anything regarding how he knows the electrical source was faulty. That “proofs” could lay the blame on “the electrical source”, while lack of such proof leads to no one to blame. The way I read it, number (b)3 is pretty clear - that coverage is excluded. I’d also note, he never said he was at a campground, he may be his own “faulty source”. Wouldn’t be the first time a do-it-yourselfer wired an RV plug wrong.

You might get something from the insurer of the faulty source (i.e. the rv park that provided the faulty source).

What does your auto policy say? Read the policy to find the coverage and then read the exclusions. That's your contract and your insurer isn't going to pay for anything outside of what's covered by the contract.