A tune-up is a measurement, not a look around. If nobody put gauges on the system or a meter on the capacitor, it was not a tune-up. Here is the full task list, what each item prevents, and the one question that tells you whether the work was actually done.
Key Takeaways
- A real tune-up is measurement, not a look around. If nobody put gauges on the system or a meter on the capacitor, it was not a tune-up.
- Ask for the numbers afterwards: refrigerant pressures, temperature split, capacitor reading. A contractor who measured has them.
- A field study of 4,168 air conditioners, cited in a Department of Energy Building America guideline, found 72% running on improper refrigerant charge. Only measurement finds that.
- A visit that takes twenty minutes and produces no readings is a sales call with a clipboard.
“Tune-up” is not a regulated term. It can mean ninety minutes of measurement and cleaning, or it can mean a filter change and a quote for a new system. Both get advertised at $89. This is how to tell which one you bought.
What should actually happen on the visit
A proper cooling tune-up takes 60–90 minutes and produces numbers: refrigerant pressures, supply and return temperatures, capacitor capacitance, and amp draw on the compressor and blower. Everything else (cleaning, tightening, flushing) follows from what those numbers show.
| Task | What it tells us | What it prevents |
|---|---|---|
| Refrigerant pressures | Whether the charge is correct and the system is sealed | Compressor failure from running undercharged |
| Temperature split | Supply against return: whether it is actually cooling | Weeks of running badly before anyone notices |
| Capacitor test under load | Whether it is inside tolerance or drifting | The most common no-cool call we take |
| Amp draw, compressor and blower | Whether motors are straining | Burnt windings; an early warning nothing else gives |
| Condenser coil clean | How much airflow the coil has lost | High head pressure and lost cooling capacity |
| Condensate drain flush | Whether the line is clearing | Water damage and a mid-summer shutdown |
| Electrical connections | Loose terminals, pitted contactors | Intermittent faults and fire risk |
| Filter | Load rate: how fast it is filling up here | Restricted airflow, frozen coil, wasted energy |
The readings, and what each number means
Numbers on a service ticket only help if you know what they are supposed to say. These are the readings a technician takes on a cooling visit, and what each one tells you about the system.
| Reading | What it tells you | Where the target comes from |
|---|---|---|
| Temperature split | How much heat the system is actually removing from the air moving through it | A typical range for a working system, read against the humidity in the house that day |
| Refrigerant charge, measured as superheat or subcooling | Whether the system holds the right amount of refrigerant, which decides both capacity and compressor life | The manufacturer’s chart for that model, not a rule of thumb |
| Capacitor capacitance | Whether the part that starts the compressor and fan still has the strength to do it | The rating stamped on the capacitor itself, with its tolerance |
| Amp draw on the compressor and blower | How hard the motors are working, and whether one is heading for failure | The nameplate on the outdoor unit |
| Total external static pressure | How hard the blower fights the duct system, filter and coil to move air at all | The blower table for that model, commonly around half an inch of water column |
Two of those targets are not fixed numbers, and that matters. Refrigerant charge is read as superheat on a system with a fixed orifice and as subcooling on a system with an expansion valve, and the target for either comes off the manufacturer’s chart for that model at that outdoor temperature.
A technician who tells you the charge is “good” without naming the method or the target has not really checked it. One who says the subcooling read 11 degrees against a target of 10 to 12 has.
The capacitor is the cheapest reading on the list and the one that most often explains a system that cools all afternoon and then refuses to restart. Capacitors fade rather than fail outright. The rating and its tolerance are printed on the can, so a meter reading below that band is a part on its way out, whether or not the system is running that minute.
Static pressure is the reading most often skipped, and it explains more comfort complaints than any other number on this list. Most residential equipment is rated to run at about 0.50 inches of water column of total external static pressure, and the rating for a given model is in its blower table. A system reading well above its rating is being strangled by ducts, a filter, or a coil, and no amount of refrigerant will fix a room that stays warm because air is not reaching it.
Those five numbers are also the reason a written ticket is worth asking for. They give the next technician a starting point, and they give you a record of what the system looked like when it was working properly.
What a tune-up is not
A tune-up is not a repair, not a warranty, and not a guarantee that nothing will fail. It is a measurement that catches the failures that announce themselves in advance, which is most of them, but not all.
Some things genuinely fail without warning. A control board can die overnight. A lightning strike does not care when your last service visit was. Anyone promising a tune-up means no breakdowns is overselling, and you should discount everything else they tell you accordingly.
Two more things a tune-up is not:
- Not a free refrigerant top-up. If a system is low, it leaked. Adding refrigerant without finding the leak is putting money into the atmosphere.
- Not a sales appointment. A tune-up can legitimately end with “this system is near the end.” It should not begin there.
How do I know the work was actually done?
Ask for the readings. A technician who measured has numbers written down; one who did not will describe the system in adjectives. It is the single most useful question a homeowner can ask, and it takes ten seconds.
Specifically, ask:
- What was the temperature split? A straight answer sounds like a number in the high teens or low twenties, in degrees.
- What did the capacitor read, and what is it rated for? Two numbers, and how far apart they are.
- What were the pressures? Two more numbers, and whether they matched the target for the day’s conditions.
You do not need to interpret them. You need to know they exist. Keep the sheet. Most manufacturer warranties require documented annual maintenance, and that record is what satisfies the requirement if you ever make a claim.
Why the spring visit matters more here
Baton Rouge runs roughly 2,625 cooling degree days a year against a US average of 1,480. Cooling is the season that breaks equipment here, so the pre-summer visit is the one that pays for itself.
National advice splits maintenance evenly between heating and cooling because in most of the country the workload is roughly even. It is not even here. A South Louisiana system spends most of the year in cooling, pulling condensate the whole time, and the failures follow that pattern: capacitors cooked by heat, coils loaded with pollen and grass, drain lines clogged with the biofilm that humidity feeds.
If budget only stretches to one visit a year, take it in spring.
What you can do yourself between visits
Three things, none of which need tools: change the filter on schedule, keep two feet clear around the outdoor unit, and flush the condensate line. Together they prevent a meaningful share of the calls we take.
- Filters. Check monthly in summer rather than trusting the box’s three-month guidance, which assumes national runtime, and yours is roughly double. ENERGY STAR recommends checking every month during heavy use and changing at least every three months.
- Clearance. Two feet around the condenser, nothing stacked on it, no shrubs grown in. It has to breathe.
- Drain line. A cup of distilled vinegar down the access tee every couple of months keeps the line clear. This is the cheapest thing on the list and it prevents one of the most annoying failures.
What to leave alone: anything with refrigerant in it, anything requiring the panel to come off, and anything involving gas. Not because it is complicated, but because the failure modes are expensive or dangerous.
HVAC tune-up questions homeowners ask us
Mostly variations on “was that a real tune-up?”, which is the right thing to be asking.
How long should an HVAC tune-up take?
Sixty to ninety minutes for a single residential system. Substantially less than that and something on the list was skipped.
What is a good temperature split?
Typically 16–22°F between return and supply air on a correctly charged system, though the target moves with indoor humidity. What matters is that your technician measured it and can tell you the number.
Is a $89 tune-up a scam?
Not necessarily. It is often a genuine loss-leader to earn your business. The question is not the price, it is whether the visit produced measurements. Ask for the readings and you will know.
How often should I change my filter in Louisiana?
Check monthly through the cooling season. A one-inch pleated filter often needs changing every 30–60 days here, not the 90 the packaging assumes, because runtime is far above the national average.
The short version
A tune-up is a measurement. If it produced numbers, it was real. If it produced a quote and nothing else, it was not.
A tune-up prevents most of this, but when a system quits between visits there is a short list worth running before you pay for a service call. Here is what you can safely check yourself first, and the point where you have to stop.
If you are weighing whether to put this on a schedule, the arithmetic is in our breakdown of whether maintenance plans are worth it, including the cases where the answer is no.
Book a tune-up and we will hand you the readings. Pressures, temperature split, capacitor, amp draw, written down, so you have the documentation your warranty needs and proof the work was done. See what is included or book a visit.
Last updated October 5, 2026
