We have an HEIL DC90 Ultra High Efficiency furnace. It randomly starts blowing out cool air instead of warm air. We live where it snows so this is a big problem. We have tried turning it off and unplugging. Sometimes it works and sometimes it doesn't. It will be working fine and then all of the sudden blowing out cold air. Do you know what could be wrong and what we could try to fix ourselves before paying a professional?
Lately while cleaning the basement, the drain hose located on the right side of the furnace was lifted about furnace height. This kept the furnace running and putting out little heat. When I lowered the hose back to the floor a small amount of water ran out. When the hose was drained the furnace works like it's supposed to. This makes me believe a lot of problems arise from the hose being plugged up, water does not run uphill and clogged the hose. I believe this may cause the furnace to malfunction. Hope this helps