I was called to a home to repair a Lennox gas furnace. Upon arrival, I found that the furnace was not producing heat. I checked the thermostat and found that it was set to "off." I reset the thermostat and tested the furnace again. The furnace started to produce heat, but it was not reaching the desired temperature. I checked the air filter and found that it was dirty. I cleaned the air filter and tested the furnace again. The furnace started to produce heat and reach the desired temperature. I also checked the gas pressure and found that it was low. I added more gas to the furnace and tested it again. The furnace started to produce heat and reach the desired temperature. I also checked the burners and found that one of them was not working properly. I replaced the burner and tested the furnace again. The furnace started to produce heat and reach the desired temperature.
