How to know when to Contact the Best Furnace Maintenance Services? Often, your home may show some signs and symptoms that there is a need for some amount of service. Like, if there is a sewer backup, you may have to call for a drain cleaning service. This is just an example. If there is some strange noise coming from an air conditioner or the furnace then you have to take some quick action. Sometimes, DIY techniques will fail and you may need specialists only to solve the trouble. But, what are the signs that would indicate that something is wrong with the furnace?