If already insured, will insurance pay for Federal Pacific Stab-Lok panel that show signs of issues? 
This is more of a maintenance issue and would not be covered under most policies . The standard homeowners policy covers you for direct physical damage to property which is sudden and accidental in nature . If the Stab-Lok panel does malfunction and cause damage to your property , the ensuing damages would be covered . Homeowners insurance is not intended to assist with the maintenance of the home and its systems . 