Today we came out for main level not heating Lennox 2014 45k with matching 1.5 ton ac. Previous company say gas valve had failed, cycled equipment from thermostat found igniter energizing but control board not sending 24 volts to gas valve main control board has failed. Found collapsed 12” main return performed safety check on furnace inspected heat exchanger with digital camera found multiple cracks. Recorded pictures, made movies and showed client findings. Scheduled install supervisor to give options on updating and left band aid repair option. Left system off at thermostat