Gas furnaces sometimes have problems staying on. One of the most common problems is when the furnace starts then stops (also furnace turns on and off). If this is happening to you, then you can do one thing to possibly solve the furnace starts then stops issue - simply change the air filter! The air filter filters out the air that your furnace is heating up and blowing through the air ducts. If the air filter becomes too clogged with dust and other particulates, then the amount of air that flows through the filter is reduced. A dirty filter can cause a furnace to overheat. When that happens, the limit switch is activated, and the furnace shuts off. If it happens too many times during the day, it might be necessary for a trained HVAC contractor to come out and reset the limit switch.
If your furnace starts then stops, the first thing you should do is change out the air filter. If changing the air filter does not solve the problem, then it is time to contact an HVAC professional. The problem may be a cracked heat exchanger, and that requires a contractor to fix it.
If you have any additional questions about gas furnaces, contact your local HVAC contractor.