Not your problem to fix
Not your problem to fix
Whatever you do, do not fix anything yourself. It's the landlord's responsibility, and you don't want to be mixed up in it. Your sister should probably consult an attorney specializing in landlord-tenant problems, because the law varies from place to place. However, it is likely that your sister is not obligated to pay rent as long as a building code violation creating an unsafe condition exists on the property. The FPE panels are not a code violation, and there is probably no legal means to force the landlord to replace them. However, it sounds as if the pool wiring was probably not compliant at the time it was installed. If that is the case, then the landlord may be compelled to repair it before collecting any further rent. However, your sister should probably seek legal advice before withholding rent.