Check the filter, if dirty replace immediately, recommend every 3-6 months replace standard 1” or 2” filters. Most larger filters 6-12 months. Check thermostat for correct setting. If digital display is out, open thermostat and replace battery. Wherever the furnace or heating unit is located, there is usually an on/off switch nearby (looks just like a light switch). Sometimes this switch gets shut off. If furnace is not working, check to make sure this switch is in the “ON” position. […]