The capacitor is a small cylindrical component that gives your compressor and fan motors the jolt of electricity needed to start. When it fails, the compressor can't start — so the fan runs but no cooling happens. You may hear a humming or clicking sound from the outdoor unit.

The contactor is a relay switch that sends power to your compressor when the thermostat calls for cooling. A worn or burned contactor means the compressor never receives power — the indoor fan runs, air moves, but no cooling occurs.

Refrigerant is the substance that actually absorbs heat from your home's air. If your system has a leak, refrigerant levels drop and your AC loses the ability to cool. Signs include: ice on the refrigerant lines, hissing sounds near the outdoor unit, and gradually worsening cooling over days or weeks.

The evaporator coil (inside your air handler) can freeze solid when airflow is restricted or refrigerant is low. A frozen coil blocks all heat transfer — your AC runs but can't cool. You may notice ice on the refrigerant lines coming out of your indoor unit, or reduced airflow from vents.

A severely clogged filter restricts airflow so much that the system can't move enough air across the evaporator coil to cool your home. In Arizona's dusty environment, filters clog faster than in most states — especially near construction zones or unpaved roads.

Before calling anyone, verify your thermostat is set to COOL (not FAN or HEAT) and the temperature setpoint is at least 3–5 degrees below the current room temperature. This sounds obvious, but it's the first thing Bradford checks on every call.

The compressor is the heart of your AC system. When it fails, the system runs but produces zero cooling. Compressor failure is more common on systems over 10 years old, especially those that have run with low refrigerant for extended periods. Signs: outdoor unit runs but makes loud grinding or clanking sounds.