When cooling quits in a heat wave, you need two things: someone who answers, and a straight answer. We're built for both.
Our rule of thumb is on paper, not in the salesman's head: age of system times repair cost, weighed against efficiency gains and the failure we just diagnosed. Somewhere past year twelve with a compressor-grade repair, replacement usually wins. Before that, we fix it and leave. You'll get both numbers and our recommendation - and it's your call.
Replacements are sized with a Manual J load calculation - the biggest system is not the best system, and short-cycling oversized units die young and dehumidify badly.
Airflow or refrigerant, almost always - a choked filter, failing blower or a leak. Running it frozen kills compressors; shut it off and call.
No-cool calls jump our queue, maintenance-plan members jump it twice. We staff up for the season instead of apologizing through it.
What the load calculation says - we measure the house, not the old unit's sticker. Bigger is genuinely worse.