Furnaces don’t see nearly as much use as air conditioners do in the Inland Empire, where winters are mild and extremely brief. But we still need them during this time of year, when temperatures can get quite chilly (especially late at night). And it can be easy to overlook the signs of trouble with your furnace, especially if they don’t result in a flat-out shutdown. If you have an older furnace and you spot signs of trouble, you may want to consider replacing it before too much time goes by.