With temps starting to dip into into the 40s at night, you may be tempted to run your furnace. And while conserving energy is great -- its actually a good idea to get the ole furnace running sooner rather than later. Testing your furnace out before winter hits is a wise choice, as it allows you to make sure there arent any leaks, odd smells or issues. Here are 3 things every homeowner should do to make sure the furnace is running in tip-top shape: 1. Change the furnace filter. When yo...