You’ll want to check for the date it was made. This is typically situated on a label on the outside of your unit.
If your system is under five years old, it may still be warrantied. At the same time, warranty terms and conditions vary between manufacturer and installing company.
At D & K Heating Service Experts, we can confirm your warranty state with a system inspection. We also have HVAC service memberships in Belleville for residential heating and AC equipment, regardless of system age or manufacturer warranty validity.