You’ll want to look for a production date. This is usually found on a label on the outside of your unit.
If your unit is less than five years old, it may still be warrantied. However, warranty terms and conditions vary between manufacturer and installing company.
At Air Engineers Service Experts, we can check your warranty standing with a system inspection. We also have HVAC service memberships in Jacksonville for residential heating and cooling units, regardless of equipment age or manufacturer warranty standing.