Not only would I argue that the burden of this duty is not on the owner, I'd suggest that any conclusion he makes is going to be completely irrelevant, unless the owner happens to be a fire investigator, insurance adjuster, or engineer with experience in agricultural or automotive electrical systems. Credentials are everything, when supplying testimony on any accident or fire, and only the conclusions made by a disinterested third party will be received without serious skepticism.
I've never sued anyone for anything, although I've had to employ lawyers several times for my business and real estate transactions. Given the value and age of the item in question, and the dealer's implication that this is his problem on a nearly new in-warranty machine, this is one case where my first stop after the dealer would have been a lawyer. If the OP hasn't already gone that way, and also followed through with at least getting his injuries documented by a doctor, I'd suggest again he do that now.