The warning signs are usually a pattern
One failed capacitor is different from three repairs in two summers. A slightly warm room is different from a system that runs all afternoon and never reaches the thermostat setting. Start keeping notes when you see repeated breakdowns, rising electrical use without a rate or lifestyle change, refrigerant leaks, worsening noise or uneven cooling that cannot be corrected through airflow work.
A diagnosis should come before a replacement pitch
Ask what failed, what caused it and what else was tested. A dirty coil or airflow restriction can make an otherwise serviceable unit look exhausted. On the other hand, a failing compressor in an older system with obsolete refrigerant may make another repair difficult to justify.
The contractor should also look beyond the outdoor unit. Duct condition, return-air capacity, electrical service and actual house load affect whether new equipment will perform better.
Plan before the first 105-degree breakdown
If the current system is operating but the repair history is getting uncomfortable, collect replacement options before summer. That gives you time to compare sizing and installation scope without making a decision from a hot house.
If the unit still cools reliably, keep maintaining it and watch the trend. Replacing working equipment solely because of age is not always the best use of the budget.
Start with AC diagnosis or review installation planning . Call 520-303-3220 for a Tucson evaluation.