Found blown fuse and failed thermostat. I replaced the thermostat with the landlords permission. I tested the heating and cooling and verified that the hvac system was operating at the end of service call. Warning furnaces on upstairs floor are over 20 years old and are in poor condition. The furnaces heat exchangers are in poor condition. The Furnaces maybe a potential fire/carbon monoxide hazard if the old exchangers were to fail in the future. In the Techs expert opinion the landlord should have them replaced asap for safety reasons.