HVAC in Las Vegas is refrigerated cooling that carries a very long season, with heat as a short side job. Condensers sit on hot pads in full sun. Air handlers sit in attics that are hotter than the driveway. The system does not get a gentle month in the middle of summer, and a weak afternoon is not something the night will fully forgive. Filters load with windblown dust and construction grit. This is not a Tucson cooler city. Some older houses still have evaporative units, and they should be named as such, because the diagnosis is pads and water, not refrigerant.
Say the symptom. No cooling, cooling that runs and loses, a frozen line, a breaker trip, or water at the ceiling under the handler. The ceiling stain is often condensate, and in a city this dry it gets mistaken for a miracle roof leak. Ask what is ruled out before a compressor is blamed: filter, airflow, capacitor, contactor, drain. A packed filter can counterfeit a major failure. If the heater is the problem, say that too. Furnaces and heat pumps here are real in winter and usually not the thing that makes a house unlivable. Still say if there is no heat on a cold desert morning.
Replacement should be sized for this house and this attic, not copied off a faded nameplate. Ask whether the indoor and outdoor equipment are a matched pair. Ask whether the ducts are in the scope, because attic ducts in this valley leak and cook. Ask about the electrical circuit, the disconnect, and where condensate will go so the next clog misses the drywall. Pool equipment is not the house system, but it shares a panel. Mention it if breakers have been a fight.
If the house is hot now, make the call now. Say what is on the pad. Call the number on this page.