Heil furnace installed 3 years ago by a business in Rochester New York. High heat advisory code 126 coming since than. They came and said nothing wrong with it. four furnace repairmen could not fix the problem. I called Gene Kring to repair, from Redwood New York He came and checked wiring, took pics of settings. He called Carrier maker of the furnace. They told him it needed more air intake. He returned and installed another intake on the plenum. Problem solved. I recommend him highly, good work, and affordable.