The Parts of a Central Air Conditioner

Central air is two cabinets and the duct system between your rooms and those cabinets. The thermostat is the switch. The cooling happens in the refrigerant circuit and the air happens in the blower and the ducts.

Outdoor unit

The condenser coil wraps the cabinet. The fan pulls outdoor air through that coil and throws the house’s heat outside. The compressor pumps refrigerant. The contactor and the capacitor are the electrical parts that let the compressor and the fan start. If this cabinet is silent while the thermostat is calling, cooling is not happening, even if the indoor blower is running.

Indoor coil, blower, and drain

The evaporator coil sits above the furnace or inside the air handler. Warm house air crosses it, the refrigerant boils, and the air leaves colder. Water condenses on the coil and should leave through the drain. The blower is the fan that moves that air. It may be a newer ECM or an older PSC motor. A filter in front of the blower is what keeps the coil from becoming a felt blanket.

Lines, thermostat, and ducts

Two copper lines connect the cabinets. The larger one is cold and insulated in cooling. Ice on it is a symptom, not a part you chip off. The thermostat is low voltage. It asks. It does not contain the compressor. Ducts and plenums deliver the air. A perfect outdoor unit cannot fix a supply duct that has fallen off in the attic.

When you call, saying which part is quiet, which grille is weak, and whether there is ice or water saves a guessing game. That is the start of AC repair. Sizing and replacement are a different conversation, after the house and these parts have been looked at.

Common questions