Keep it running6 min readSeptember 22, 2026
What a real HVAC tune-up includes, and how to spot a sales visit in disguise
A real tune-up measures things: refrigerant charge by superheat and subcooling, capacitor microfarads against the rating, motor amp draw, temperature split, static pressure, and on furnaces the ignition sequence, flame sensor, heat exchanger and carbon monoxide. It cleans the drain line and the coils if needed, and it ends with the readings in writing. A visit that produces no numbers and a replacement quote was a sales call.
The cooling checklist
Ask for these by name. A technician who does them will not mind the question.
- Refrigerant charge measured by superheat or subcooling, not by looking at a gauge for a second
- Capacitor tested in microfarads against the rating printed on it; replaced if it is out of tolerance
- Contactor inspected for pitting; compressor and fan motor amp draw against the data plate
- Temperature split between return and supply, which should land in the 15 to 20 degree range on a healthy system
- Static pressure across the air handler, which tells you whether the ducts and filter are choking the blower
- Indoor coil inspected and outdoor coil rinsed
- Condensate drain flushed and the float switch tested
- Thermostat calibration and wiring at the board tightened
The heating checklist
- Ignition sequence timed and the flame sensor cleaned
- Burners inspected for alignment and rust; gas pressure checked where accessible
- Heat exchanger inspected for cracks, with a carbon monoxide test at the supply with the blower running
- Limit switch, pressure switch and rollout switches tested
- Inducer and blower motors checked for noise and amp draw
- On heat pumps: defrost cycle, reversing valve and backup heat strips tested
What you should walk away with
A written list of the readings and what they mean, a note of anything that is out of range and a price to fix it from a published book, and a straight statement of the system's age and condition. Not a verdict. A tune-up on a 15-year-old system can perfectly well end with: everything is in range, see you in the fall.
How the cheap tune-up works
The $29 and $49 tune-ups advertised around DFW lose money on the visit and make it back on what the visit finds. The technician is usually paid a commission on repairs and replacements sold, so the visit ends with a list of problems and often a replacement quote. Some of the problems are real. The way to tell is to ask for the readings: a capacitor that reads 38 microfarads against a 45 rating is a real finding, and a company that cannot show you the number is selling.
Questions on this
Does a new system need tune-ups?
Yes, and most manufacturer parts warranties require documented annual maintenance to stay valid. Keep the reports.
Is twice a year really necessary?
Once for cooling and once for heating is the standard because the two sides use different parts. A house with no gas furnace and a well-kept heat pump can often do one thorough visit a year.
How long should it take?
Forty-five minutes to an hour and a half per system. A fifteen-minute visit did not measure much.