What does an AC tune-up include?

A proper spring service on a Houston system has a list, and you should be able to see it written down afterwards. Outside: the condenser coil cleaned, the fan motor checked, the capacitor and contactor tested with readings, the refrigerant charge checked against the manufacturer's figures for that unit on that day's conditions, and the disconnect and wiring inspected. Inside: the filter, the blower, the evaporator coil as far as it can be seen, the condensate drain flushed and the float switch tested, and the thermostat checked.

Two of those earn their keep every year in Houston: the condenser cleaning, because a dirty coil can cost a fifth of the system's capacity in August, and the drain flush, because a clogged drain in July puts water through a ceiling.

What a tune-up should not be is a pretext for selling a system. If the technician recommends replacement, ask for the readings that led him there, and if he cannot show them, get a second opinion in writing.