Performed furnace diagnostic, heat only furnace, with new tstat. Found blown low voltage fuse. And loose wire connection inside unit. Replaced 3 amp fuse and tightened g wire. Then tested system. System runs need to to keep an eye on the blower capacitor, and inducer motor sounds rough. Also with age of equipment want to watch how much money we are putting into system, Regular maintenance of system System, furnace only in closet, swamp cooler on roof. And plumbing. Plumbing inspection would like soon. Inbetween tenants at this time.