What Happens During an HVAC Tune-Up? (Everything a Tech Checks)

What Exactly Is a "Tune-Up"?

The term "HVAC tune-up" gets used loosely in the industry. To some contractors, it means a 20-minute visit where a tech changes your filter and leaves. To us, it means a systematic 60–90 minute inspection of every component that affects your system's performance, safety, and lifespan.

Here's exactly what a qualified technician checks — and why each item matters.

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Air Conditioner Tune-Up: Complete Checklist

Electrical System Inspection

Capacitors — tested with a capacitor meter

Capacitors are arguably the most failure-prone component in an AC system. They store electrical charge to start the compressor and fan motors. As they age, their capacitance drops below the manufacturer's specification — the motor still starts, but it strains to do so, drawing excess current and overheating.

A meter test reveals the exact capacitance value. Manufacturers allow a ±6% tolerance. Anything outside that range means the capacitor should be replaced before it fails — usually on the hottest day of the year.

Contactors — inspected visually and tested

The contactor is an electrical relay that turns the compressor and condenser fan on and off in response to the thermostat signal. Over time, the contact points pit and burn from repeated electrical arcing. Severe pitting can cause the contactor to weld shut (the compressor runs continuously even when not called for) or fail to close (the compressor won't start at all).

Electrical connections — inspected and tightened

Vibration from normal operation loosens electrical connections over time. Loose connections create resistance, which generates heat. A technician inspects all wire connections in the electrical disconnect, control board, and terminal blocks — and tightens any that have worked loose.

Disconnect and circuit breaker — verified

The outdoor electrical disconnect is checked to confirm it can be safely shut off for service. Fuses are tested if present. The circuit breaker amperage is confirmed to match the equipment's nameplate requirements.

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Refrigerant System Check

Refrigerant level — checked with digital manifold gauges

Low refrigerant (undercharge) reduces cooling capacity, causes the evaporator coil to ice up, and eventually damages the compressor. High refrigerant (overcharge) causes high head pressure and compressor damage through liquid slugging.

A technician connects digital manifold gauges to the service ports and reads suction and discharge pressures. These are compared against manufacturer specifications for the current ambient temperature to determine whether the charge is correct. If low, a leak must be found and repaired before refrigerant is added — simply adding refrigerant to a leaking system is both wasteful and an EPA violation.

Refrigerant lines — inspected for damage and leaks

Copper refrigerant lines are checked for oily residue (a sign of refrigerant leaks), damaged insulation, and adequate support.

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Coil Cleaning and Airflow

Condenser coil — cleaned

The outdoor condenser coil releases heat from the refrigerant into the outdoor air. A coil caked with dust, cottonwood seeds, or debris can't release heat efficiently — the system runs hotter, works harder, and uses more electricity. Cleaning involves applying coil cleaner and rinsing with water.

Evaporator coil — inspected and cleaned as needed

The indoor evaporator coil absorbs heat from your home's air. Because all of your home's air passes over this coil, it accumulates dust and debris that slip past the filter. A dirty evaporator coil reduces heat transfer efficiency and can cause the coil to freeze solid.

Evaporator coil cleaning is more involved than condenser cleaning because the coil is enclosed in the air handler. Mild buildup is addressed with a no-rinse coil cleaner during the tune-up. Heavy buildup may require a separate service visit.

Condenser fan motor and blades — inspected

The condenser fan motor is checked for proper operation, correct amperage draw, and any unusual vibration or noise. Fan blades are inspected for cracks, bends, or debris that could cause imbalance.

Blower motor — tested and measured

The indoor blower moves air through your duct system. It's tested for correct speed (many systems have multiple speed settings), proper amperage draw, and clean operation. A dirty blower wheel (the squirrel-cage fan) is a common, overlooked problem that reduces airflow significantly — even when the filter is clean.

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Drainage System

Condensate drain line — flushed and treated

Your AC removes moisture from the air as it cools — often 2–5 gallons of water per day in humid conditions. This water drains through a condensate line. Algae, mold, and debris clog this line regularly, causing water to back up into the drain pan and potentially overflow into your home.

During a tune-up, the drain line is flushed with water and treated with algaecide tablets or a diluted bleach solution to prevent future buildup. The float switch (which shuts off the system if the pan fills with water) is also tested.

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System Performance Test

Temperature split — measured

The technician measures the temperature of air entering the return duct and exiting a supply vent. The difference — called the temperature split or delta-T — should be 18–22°F for a properly operating system. Too small a split indicates low refrigerant, dirty coils, or airflow problems. Too large a split indicates the system may be oversized or has restricted airflow.

Superheat and subcooling — calculated

For fixed-orifice systems, superheat is measured to confirm refrigerant charge. For TXV systems, subcooling is measured instead. These calculations, combined with refrigerant pressures, give the technician precise data about system performance.

System operation in both modes — verified

The system is run in cooling mode and, if applicable, heating mode. Thermostat staging is confirmed to be working correctly.

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Furnace Tune-Up: Complete Checklist

If your appointment covers the furnace as well, here's what's inspected:

Heat exchanger — inspected with camera or light

The heat exchanger separates combustion gases from your breathable air. A cracked heat exchanger is a carbon monoxide hazard and typically means furnace replacement. A thorough visual inspection (often with an inspection camera) is performed on every visit.

Burners — inspected and cleaned

Gas burners are checked for proper flame color (blue with stable shape — not yellow or lifting off the burner), carbon buildup, and even ignition across all burners.

Igniter or pilot — tested

Hot surface igniters are tested for resistance (they become brittle with age and can crack). Pilot lights are checked for proper flame position.

Gas pressure — measured

Manifold gas pressure is checked against manufacturer specification. Incorrect gas pressure affects combustion efficiency and can cause safety issues.

Flue system — inspected

The flue pipe is checked for proper slope, secure connections, and no obstructions. Carbon monoxide detectors in the home are noted.

Filter — replaced

The air filter is replaced at every tune-up (filter cost is typically included or charged separately at cost).

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What Happens After the Tune-Up

At the end of the visit, a qualified technician will:

1. Walk you through any findings — items that were addressed, items to watch, and any recommended repairs
2. Provide a written inspection report
3. Show you anything physically accessible and explain what they found
4. Answer your questions without pressure

Red flag: If a technician finds "problems" on every visit, or discovers a critical failure on an otherwise young, well-maintained system, ask for a second opinion.

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How to Get the Most from Your Tune-Up

Schedule in spring and fall — before each season's peak demand, not during it.

Write down any symptoms — unusual sounds, hot or cold spots, or smells you've noticed. Even intermittent symptoms give the technician useful diagnostic information.

Be home — many technicians won't enter an attic or crawlspace alone without someone present in the home. Your presence also allows them to demonstrate findings directly.

Ask for the inspection report — a thorough technician should provide written documentation of everything checked and found.

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Schedule Your Tune-Up

We perform comprehensive HVAC maintenance for AC systems, furnaces, and heat pumps throughout the Bay Area. Our tune-ups include a written 25-point inspection report and no-pressure findings review.

Schedule your HVAC tune-up → | Learn about our maintenance services →

(925) 578-3379 | Licensed CSLB #1076868 | NATE Certified