Sometimes a furnace simply needs a good cleaning and a little maintenance to get it in full working order. But, sometimes it is going to cost more to fix the problem than to replace the entire unit. In that case, we recommend replacing your old gas furnace with Goodman GMSS921205DN 120000 BTU 92% AFUE 1 Stage Upflow Gas Furnace. This high-quality, efficient gas furnace employs a reliable dual-diameter tubular heat exchanger design and a durable silicon nitride ignitor. It has a quiet single-speed induced draft blower, a self-diagnostic control board, and a heavy-gauge steel cabinet with a durable finish. It also complies with California's 40 ng/J Low NOx emissions standard.