What actually happens in an AC tune-up

Maintenance is the easiest service in this trade to do badly, because almost nobody watches. A technician can spend forty minutes going through a system properly or eight minutes hosing off the outdoor coil, and from the homeowner's side of the door those two visits look identical. Both end with an invoice and a sticker on the unit.

The only real defence against that is a published list. Below is what gets checked on each type of equipment, so you can read it before a visit and check it afterwards. It is not a secret and it is not proprietary. It is just the work.

The air conditioner

• Clean condenser coil
• Inspect evaporator coil if accessible
• Clean condensate drain
• Clean blower motor
• Inspect filtration system
• Adjust blower components
• Inspect for refrigerant leaks
• Test condensate pump
• Tighten electrical connections
• Test starting capabilities
• Measure air temperature differential
• Monitor refrigerant pressure
• Measure amperage and voltage

Several of those are worth understanding rather than just ticking. Tightening electrical connections sounds like nothing, but connections work loose across a season of vibration and thermal cycling, and a loose connection produces heat, which is how contactors burn and how avoidable failures start. Testing starting capabilities means checking that the compressor can actually get going under load, which is where a weakening capacitor shows up first. And measuring amperage and voltage every year builds a record, so next year's numbers can be compared against this year's rather than judged in isolation.

The air handler

• Inspect evaporator coil
• Clean blower motor
• Inspect filtration system
• Adjust blower components
• Test and adjust safety controls
• Tighten electrical connections
• Inspect humidification system
• Inspect electrical heating elements

The furnace

• Test for carbon monoxide leaks
• Clean burner assembly
• Clean ignition assembly
• Clean blower motor
• Inspect filtration system
• Adjust blower components
• Test and adjust safety controls
• Tighten electrical connections
• Check flue draft
• Check combustion
• Inspect vent piping
• Inspect humidification system

The furnace list opens with the carbon monoxide test, and that ordering is deliberate. Every other item on the list is about performance and cost. That one is about whether the appliance is safe. When fuel does not burn completely, carbon monoxide is one of the products, and it is odourless. Checking the flue draft, the combustion and the vent piping are all part of the same question: is everything that should be leaving the house actually leaving it. We recommend carbon monoxide detectors in every home with a gas appliance, regardless of how new the equipment is.

The heat pump

• Clean condenser coil
• Clean condensate drain
• Check defrost controls
• Inspect auxiliary heaters
• Inspect filtration system
• Inspect for refrigerant leaks
• Test condensate pump
• Tighten electrical connections
• Test starting capabilities
• Measure air temperature differential
• Monitor refrigerant pressure
• Measure amperage and voltage

Why any of it is worth paying for

Maintenance is a hard sell because its entire value is in things that did not happen. Nobody feels the breakdown they avoided. What you can observe is narrower: the system holds its efficiency instead of drifting downward, the power bill stops climbing year on year for no visible reason, and small faults get caught while they are still small.

Neglect works the other way and it works quietly. Performance declines steadily while energy use rises, and because it happens over years rather than weeks, most people never register it as a change. They simply come to accept that the house takes a long time to cool and the summer bills are what they are.

How often, and what to do between visits

Once a year for cooling, once for heating. In Houston it is tempting to skip the heating side, since the furnace runs a handful of weeks a year, but that idleness is exactly the problem: ten months of dust settling on burners and blowers, and then the first hard cold snap when every system in the region is asked to start at once.

Between visits, the single most useful thing you can do is change the filter regularly. How often depends on the filter type, whether you have pets, and the size of the equipment, so it is worth asking rather than guessing. A restricted filter makes the whole system work harder to move the same air, and it undoes a good deal of what a tune-up achieved. If you want the reminding taken out of your hands entirely, an annual service agreement does that, and it is what most of our repeat customers end up on.