HVAC And The Basement Smell

Have you ever smelled the smell of a basement? If you have an unfinished basement, you probably know what I'm talking about.  Half of my house sits over a crawl space with a dirt floor. So imagine your basement smell inside your living area now. Not as strong as the basement, but you still notice it.
My house is an older house. Some people have said that it's just the way an older house smells. Well, I don't think that having the smell of your basement is normal. Or, it shouldn't be.  So I set off to fix this issue.
First, I called my HVAC guy. He came out and really didn't do much. And he charged me $75 for coming out. And, the smell was still coming through the HVAC when he left.
Next, I decided to pursue it myself. So, I ended up in the basement in the crawl space. I ended up finding an intake duct run that was slightly disconnected from the vent up on the main floor. Once I connected it back up and taped it up, I found that the problem of the smell upstairs was resolved.
Here is the interesting thing though. When we want to keep it cold at night for sleeping, we normally keep it at 69 to 70 degrees. Now, after fixing this intake issue, 73 degrees is too cold. Even tonight, 74 degrees was too cold. We have noticed that the efficiency of the HVAC system is much better now. All it took was for me to go down and examine the whole duct system and correct any problems that I saw. Now, our unit is doing much better.