I do not know where to start. I called air control heating and cooling because, I was having issues with my thermostat. The tech said that my thermostat was the issue. I agreed for him to replace the thermostat, I am grateful that once the technician fixed the problem with the thermostat he then recommended a furnace tune up . The price was reasonable so I agreed. The technician called me down stairs and showed me a crack on my heat exchanger. I am so grateful that the technician was straight forward and honest with me. The technician told me it will be better to replace because furnace was 22 yrs old. If this would have gone unknown , who know what have been the out come. Thank you my house is nice and warm again