One of the most common issues in early winter, are Gas furnaces that wont stay running! They repeatedly cycle on and off, only heating for 2-5 minutes. This is commonly referred to as Short Cycling.
You may have a gas furnace thats several years old yourself. During a cold snap the furnace won't heat the house to desired temps. It will turn on, ignite and provide heat for a short period of time and then turn back off, after only a few short minutes of relief.
Many people jump right at replacing the thermostat, hoping it will fix the issue, but alas, its not likely the problem. You may see a flashing light which is a diagnostic code and may flash 3 or 4 times. You can refer to your user manual, which is usually left on top of the furnace, to diagnose these codes. Many short cycle issues are caused by something simple like a dirty flame sensor.
Short Cycling is caused by one main thing- your furnace overheating, and the safety mechanisms, automatically shutting it down. Regardless, it should be treated as a very serious problem as there have been cases of leaky heat exchangers causing this to occur as well.
One of the first things to check is that you have adequate airflow going to the unit. Check all your filters and make sure they are allowing air to pass through. If they are dirty, replace the filters and try the unit again. If this makes no difference, check to be sure hot air is not blowing directly onto your thermostat, causing the call for heat to be met soon after the unit turns on.
If all else fails, you are much better off calling out a service company to come and diagnose the problem for you. There are simply too many areas that need to be considered, for a homeowner to diagnose on their own. Always check with Angies List before calling a contractor. You will find unsolicited reviews from people just like yourself of the best contractors in your area, as well as the costs that people paid for the work.
If you know what is broken and want to attempt the repair on your own, take a look through our eBay store for the Furnace Replacement Parts at quite a discounted price!