Sure. This is the relevant clause in my current home insurance policy:
"You must take steps to maintain the Home in a good state of repair and take all reasonable precautions to avoid loss, damage or injury and to safeguard all property insured from loss or damage."
These things are pretty standard - I would be very surprised if there isn't a similar clause in all of them.
Which implies that, if you fail to do so, they don't have to pay up.
The wording in your policy may be different. What are "reasonable steps" will depend on legal precedent. It may, for example, take into account that you're not an expert, and will probably include some reasonable time to get stuff fixed. But certainly it provides them the opportunity to deny a claim.
Obligatory disclaimer: I am not a lawyer or insurance expert, get your own advice if you need it.
It seems plausible that not addressing the electrical anomaly described by nicolaslem could be called a failure to maintain the home under your policy.
For completeness, the relevant section from my policy is "We will not pay for any loss to the property...as a result of...Neglect, meaning neglect of the insured to use all reasonable means to save and preserve the property at and after the time of a loss, or when property is endangered". But in the same context, it says "However, we will pay for any resulting loss from ... defect, weakness, inadequacy, fault, or unsoundness in ... design, specifications, workmanship, repair, construction, renovation, remodeling, grading or compaction; [or] maintenance."
It would be shaped by the legal precedent in interpreting these sorts of clauses, and perhaps also the whims of a jury. It still seems unlikely to me that either of our policies would end up excluding the electrical anomaly, and moreover I've yet to ever hear a verifiyable account of someone whose homeowners insurance claim was denied after an electrical problem in their house led to a loss.
I don't know if that exact case can be found, but it's a fairly obvious generalisation of the general principle. that if failure to repair in a timely way a fault or delapidation can result in reasonably forseeable further damage, insurers will be very reluctant to write policies cover the further damage; because it would result in moral hazard in the purchaser of insurance. So I would personally not like to rely on it being covered (apart from the obvious risk to the person of the house burning down).
That's not to say that the original electrical fault wouldn't be insured - that depends on other terms.
Your policy does seem to be more lenient than mine in that it allows "resulting loss from " ... "inadequacy or unsoundness in" ... "maintenance". I wonder what the scope of that is in reality.
