How to Prepare Your AC for Summer: Complete Checklist

Every spring, I get asked the same question: "What should I do to get my AC ready for summer?" The honest answer is that there are exactly seven things a homeowner should do, and twenty-one things a competent technician should measure on an annual tune-up. The difference between those two lists is the difference between a system that limps through August and a system that runs at its design efficiency.

This is the actual pre-summer AC readiness protocol I follow on customer systems in Torrance, Redondo Beach, Manhattan Beach, El Segundo, and the rest of the South Bay corridor. It's the list, in order, with the measurement tolerances that matter.

Why "Tune-Up" Is Mostly Theater (Without Measurement)

The HVAC industry has a quality problem with maintenance services. A typical "tune-up" sold by national chains and franchise operators consists of: visual inspection, hose-down of the condenser, filter replacement, and a checklist sticker. None of those steps measure anything. None of them reveal a refrigerant slow-leak, a degrading capacitor, an out-of-spec contactor, or a duct leak.

A tune-up that doesn't include numbers is a tune-up that doesn't catch problems before they become repairs. Demand the numbers. If your maintenance contractor can't email you a report with refrigerant pressures, subcooling, superheat, blower amp draw, capacitor microfarads, and static pressure, you are paying for theater.

The Homeowner's 7-Step Pre-Summer Checklist

Before a technician arrives — or in lieu of one if your system is under three years old — here is the homeowner-doable list:

1. Replace the Air Filter (Correctly)

Match the filter type and size to the system spec. A 1-inch fiberglass filter in a system designed for a 4-inch media filter cabinet will starve the blower of airflow. A MERV 16 filter in a system designed for MERV 8 will increase static pressure beyond the blower's curve. The factory-spec replacement filter for your system is the right answer.

For most South Bay residential systems built since 2005, the right answer is a 4-inch MERV 11–13 media filter (Aprilaire 213, Honeywell FC100A, or equivalent). Replace every 6–12 months.

2. Clear Two Feet Around the Condenser

The outdoor unit needs two feet of clearance on all four sides for proper airflow. Trim back hedges, remove pool toys, sweep leaves. A single bag of leaves matted against the condenser can drop capacity 15%.

3. Rinse the Condenser Coil with a Garden Hose

Low-pressure water from the *inside out* — open the top grille if accessible, spray downward through the coil. Never use pressure washers; they bend fins and create internal coil damage that's invisible until your tech finds it next year.

For coastal homes within a mile of the ocean, this rinse should happen quarterly. The salt deposits accelerate corrosion if left in place.

4. Test Your Thermostat

Set the thermostat to "cool" and 5°F below room temperature. The system should kick on within 60 seconds. If it doesn't, the issue is thermostat, low-voltage wiring, or contactor — none of which are DIY territory. Don't try to "fix" a thermostat that's not responding.

5. Walk Every Supply Register

Open every supply register. If any are closed or partly blocked by furniture/drapes, you're starving zones and pushing the blower into a higher static-pressure regime than designed.

6. Check the Condensate Drain Line

The condensate drain typically exits at a tee near the indoor air handler. Pour a gallon of water through the condensate pan; it should drain within 30 seconds. If water backs up, the line is clogged. A clogged condensate line will trip the float switch and shut the system down — usually on the hottest day of the year. A few seconds with a wet/dry vacuum at the outdoor termination, or 1/4 cup of distilled white vinegar at the indoor cleanout, prevents this.

7. Listen On First Startup

Stand near the condenser when the system first starts for the season. Normal startup: a click (contactor), then the compressor and condenser fan motor spool up smoothly within 3 seconds. Abnormal: hum without rotation (start capacitor failed), grinding (compressor bearing wear), buzzing (contactor pitting). If you hear any of these, shut the system off and call a tech *before* you run it for an extended period.

The Technician's 21-Point Protocol

Here is what we measure on every pre-summer tune-up. If your tech doesn't measure most of these, you are paying for a sticker.

Refrigerant Side:

1. Suction pressure at the service port — typical R-410A residential cooling: 110–130 psig at 75°F outdoor. 2. Discharge pressure — typical 250–400 psig depending on outdoor temp. 3. Superheat at evaporator — target 8–14°F for fixed-orifice systems. 4. Subcooling at condenser — manufacturer spec, typically 8–14°F. 5. Suction-line temperature — used to verify charge. 6. Liquid-line temperature — used to verify charge. 7. Refrigerant leak check with electronic detector (Bacharach H-10 Pro or equivalent) at every brazed and flared joint.

Electrical Side:

8. Compressor amp draw — should be at or below RLA on the data plate. 9. Condenser fan motor amp draw — should be at FLA spec. 10. Indoor blower amp draw — verifies airflow balance. 11. Capacitor microfarad — must be within ±6% of spec (a 45 µF capacitor reading 41.5 µF is bad, even if it "still works"). 12. Contactor visual — pitted contacts get replaced before they fail. 13. Voltage at compressor under load — checks for voltage drop.

Airflow Side:

14. Total external static pressure (TESP) — measured with a manometer at the air handler. ACCA spec is 0.5 in. wc maximum; field reality is often 0.7+ in. wc on neglected systems. 15. Filter pressure drop — high readings mean wrong filter or it's overdue. 16. Return-side static — high readings mean undersized return ducting. 17. Supply-side static — high readings mean undersized supply or closed registers.

Combustion / Heating Side (for furnaces and heat pumps):

18. Flame sensor microamp reading — needs 1.0+ µA, target 4–8 µA. 19. Inducer-motor static pressure switch verification. 20. CO measurement in supply plenum — must be 0 ppm. 21. Heat exchanger inspection with borescope camera.

A complete annual tune-up takes 90–120 minutes and produces a written report. If your tech is in and out in 30 minutes, none of this is happening. Find a different tech.

Refrigerant Charge — Why "Topping Off" Is Almost Always Wrong

The single most common malpractice in residential AC service is "adding refrigerant" without leak detection. Refrigerant doesn't get consumed; if a system is low, it leaked. Topping off masks the leak temporarily. Two months later the system is low again, and now there's been refrigerant venting to atmosphere — which violates EPA Section 608 regulations and contributes to greenhouse-gas emissions.

The correct procedure when a system is low: pressure-test for leaks with nitrogen, identify the leak point with electronic detector or UV dye, repair the leak, evacuate the system to 500 microns or below (verified with a micron gauge, not a vacuum-pump-only measurement), then weigh in the factory-spec refrigerant charge using the data-plate target.

A "$200 refrigerant top-off" that doesn't include leak detection is a $200 service call you'll be paying again in 8 weeks.

What to Do If the System Has Been Off for 6+ Months

Heat pumps (year-round operation) don't have this issue. Cooling-only systems that have been off through winter need a longer commissioning visit:

• - Crankcase heater verification (24-hour minimum heater run before compressor start in cold conditions)
• Filter inspection (filters left in over winter often have rodent damage in coastal/inland transition zones)
• Drain pan inspection (winter dust + condensate residue → algae in spring)
• Outdoor disconnect verification (corrosion at the disconnect terminals is the #2 startup failure mode after capacitor degradation)

When To Schedule

The ideal window for South Bay pre-summer AC service is mid-March through early May. Demand spikes start the third week of May with the first sustained 80°F+ stretch, and the wait list for routine maintenance can run to 3–4 weeks by June. Customers on our annual maintenance plan get scheduled by zone in March-April; new customers should book by mid-April for guaranteed pre-Memorial-Day service.

— Daniel Cervantes, Chief HVAC Engineer, RedAlert HVAC. The numbers in this article are pulled from current ACCA and ASHRAE technical references and verified against our own field-data logs over the last seven years of South Bay service work.