The law says your landlord is responsible for keeping your place in a good state of repair. It doesn't matter if your lease or rental agreement says otherwise, or if you knew about the problem when you agreed to rent the place. Since you've already told the landlord about this problem, the next step is to put it in writing. If the landlord still refuses to fix the stove, there are other steps you can take, such as contacting your local bylaw department, or applying to the Landlord and Tenant Board for a repair order. In the meantime, make sure to keep receipts for any extra expenses caused by not having a working stove.