How do I tell if my refrigerant is low?

Determining whether your residential HVAC or mini-split cooling system is low on refrigerant requires watching for distinct performance indicators and physical warning signs. Common symptoms include your air conditioner blowing lukewarm or room-temperature air from supply vents instead of chilled air, running continuous cooling cycles without ever satisfying the thermostat, and frost or a solid block of ice forming on indoor evaporator coils or copper lines due to plummeting operating pressures. Visually, you can inspect metal lines, flare connections, and condenser coils for oily or greasy residue, because refrigerant oil escapes alongside the gas and leaves a distinct sticky film. You can troubleshoot temperatures with a digital thermometer. You can verify that refrigerant is low when professional gauge diagnostics confirm a pressure drop.