HVAC in Phoenix is the machine that keeps the house usable from late spring into fall, and it rarely gets a gentle season. Condensers sit on gravel in the full sun. Air handlers sit in attics that are hotter than the yard. Filters load with dust every time the wind rises, and a haboob can choke a system that was marginal in the morning. Nights stay warm, so the equipment does not get the recovery a Tucson house often gets after sunset. If the system is weak at four, it is often still weak at ten.
Say the symptom first. No cooling at all, cooling that runs and never catches up, a frozen line, a breaker that trips, or water staining the ceiling under the air handler. That last one is often a condensate clog, not a roof leak, and it is one of the classic Valley calls. Ask what was checked before a compressor is blamed: filter, airflow, capacitor, contactor, and the drain. A dirty filter can counterfeit a major failure. Refrigerant questions come after airflow, not before.
Replacement is a different call from a repair. Ask whether the new equipment is a matched pair sized for this house, not a copy of whatever tonnage was on the pad. Attic ducts in older houses leak and collapse, and a new condenser on ruined ducts will disappoint you in July. Ask whether the ducts are in the scope. Ask about the electrical circuit and the disconnect. Ask how condensate will be piped so the next clog does not land on the ceiling. If a heat pump or a gas furnace is part of the system, say so. Winter heat here is real for a few weeks and usually not the crisis.
Maintenance is a spring conversation, but the call you make on a failed afternoon should not be postponed for a schedule. Pads, older swamp coolers on a few central houses, and refrigerated systems are not the same equipment. Say which one is on the roof or beside the house. Call the number on this page.