There are normal signs of wear and tear on the HVAC unit. Sometimes the machine will start to make a strange sound. That sound is often the very first alert that something is wrong with the HVAC unit. There are a number of problems that can cause the machine to make different sounds and many of the problems can be fixed easily. Some of those issues may require a licensed HVAC technician. Having a top rated professional check on the issue is always the best idea. My wife and I were having some trouble with the furnace and we started hearing a strange sound. The strange and odd noise persisted for three days before we decided to call a professional. Neither one of us recognized the noise coming from the heating machine, so we decided to call a licensed and reputable company in the valley. We ended up having an appointment on the same day and we found out that the sound was coming from the furnace. We were lucky that the issue was not severe, and the repair did not cost a lot of money. The furnace repair technician told my wife and I that we absolutely did the right thing when we called the repair company. The guy suggested that it was always a good idea to call an expert when the machine starts making a strange and weird sound. That is the same advice for the furnace or the air conditioner. The signs of wear and tear can be odd smells or sounds and they are absolutely the way that the machine alerts us when there is a problem.