You’ll want to look for a manufacture date. This is usually situated on a label on the exterior of your equipment.
If your system is newer than five years old, it might still be under warranty. Having said that, warranty terms and conditions differ manufacturer and installing company.
At Service Experts Heating & Air Conditioning, we can verify your warranty state via a system inspection. We also offer HVAC service memberships in Livermore for residential heating and cooling equipment, regardless of unit age or manufacturer warranty standing.