A landlord is not affirmatively required to improve or correct wiring, other than his obligation to comply with all building codes and provide a premises which is safe to inhabit. That said, if the landlord is aware of a problem with the wiring and does not correct it, he (not the tenant) would be liable for any damages, injuries, or costs it causes. If the landlord tries to make you pay, if you can show that you have provided notice to the landlord of the problem, you should have a good defense. You may wish to also call the building department or code enforcement, and see if they will inspect and--if there's something not to code--issue a citation or otherwise force the landlord to correct the situation. The citation and inspection could also be evidence in your favor if you end up in litigation with your landlord.