The loud, banging noises you hear coming from your furnace may be caused by a number of things. If it sounds like something is hitting against the fan blade or blower wheel, this can indicate that there is debris stuck in either one of those areas. If you have a plastic cover over your furnace and it makes noise when it's moved around, then this could mean that there are gaps between where the cover fits onto the unit and some dirt has collected there.
If you hear roaring noises coming from inside your unit, then this could mean that there is too much air being sucked into through an open vent pipe or flue vent (if applicable). This will cause excess pressure which leads to blowing out hot air through cracks in pipes or joints between sections within them--you might even see smoke coming out! Whistling sounds could indicate loose bolts holding parts together; if they're not tight enough they'll vibrate while running causing whistling sound waves as well as vibration throughout entire house when operating at high speeds during peak hours (when everyone else uses their heaters).
It's time to call a specialist if you see any of the above indicators. It's critical to pay attention to these warning signs since, if ignored, they may develop into more serious issues. To avoid overreacting, call us if your furnace is making odd noises or running continuously without adequately heating your home. We'll visit you and evaluate the situation so that we can quickly get things back on track for you.