Do this before the first real heat arrives. Most of these take under 10 minutes and catch the problems that turn into a 90°F emergency service call.
The checklist
Thermostat (5 minutes, free)
1. Switch to Cool mode and run a test cycle. Set the thermostat 2-3°F below current room temperature. Within a few minutes the outdoor unit should start and registers should blow noticeably cold air. If nothing happens in 5 minutes, troubleshoot at Why Your AC Isn’t Cooling.
2. Check the schedule. Did the winter heating schedule load over your cooling schedule? Re-enter your summer setpoint schedule: 78°F home, 85-88°F away, back to 78°F in the evening.
3. Replace the batteries. Even wired thermostats often have a backup battery. A dead battery in August means a hot house. Replace now, costs $2.
4. Check sensor placement. Did anything change over winter? A new floor lamp, a rearranged couch, or a moved bookcase sitting in front of the thermostat throws off its temperature reading. The thermostat needs clear air circulation.
Air handler / indoor unit (15 minutes)
5. Replace the filter. A fresh 1″ filter is the single highest-ROI spring task. A clogged filter reduces airflow over the evaporator coil, can ice the coil, and causes short cycling. If you can’t see light through the filter, replace it. Filter type and household factors change how often — see our replacement schedule guide.
6. Clear the condensate drain. Pour a cup of water down the drain pan. It should flow freely. A clogged drain grows mold and can trip the float switch that shuts the system off — right in the middle of a heat wave. Flush with a cup of white vinegar if it seems slow.
7. Look at the evaporator coil. With the air handler access panel open, the coil is the finned surface the filter protects. Light gray dust = fine. Heavy buildup, debris, or ice = call a technician.
Outdoor unit (15 minutes)
8. Clear 2 feet around the condenser. Trim any vegetation that grew over winter. The condenser needs airflow on all sides. Remove any covers or tarps before running the system.
9. Hose off the condenser fins. A gentle rinse from inside-out (nozzle over the top, water pushing debris out through the fins) removes pollen, cottonwood, and winter buildup. Let it dry before running. Avoid bending the fins; straighten bent fins with a fin comb if needed.
10. Check that the system can hold setpoint. On the first warm day (75°F+), set to 74°F and watch whether it gets there in 30-45 minutes. If it runs non-stop and never arrives, there’s a cooling problem worth diagnosing before summer, not during it.
| # | Task | Time | Cost |
|---|---|---|---|
| 1 | Cool-mode test cycle | 5 min | Free |
| 2 | Check schedule | 2 min | Free |
| 3 | Replace thermostat batteries | 2 min | ~$2 |
| 4 | Check sensor placement | 1 min | Free |
| 5 | Replace filter | 5 min | $5–35 |
| 6 | Clear condensate drain | 5 min | Free |
| 7 | Inspect evaporator coil | 2 min | Free |
| 8 | Clear space around condenser | 10 min | Free |
| 9 | Hose off condenser fins | 10 min | Free |
| 10 | Setpoint recovery test | 45 min (passive) | Free |
A professional tune-up beyond this checklist typically includes an EPA Section 608-certified refrigerant pressure check, contactor and capacitor inspection (see AC contactor and AC capacitor), and motor amp-draw testing against the equipment’s AHRI-rated nameplate values — a fuller diagnostic pass than any homeowner checklist can replicate.
When to bring in a pro
The homeowner list above is high-impact but incomplete. A full pro tune-up (typically $75-150 in most markets) includes a refrigerant pressure check, electrical connections, motor amp draw, and coil cleaning. Worth it for systems over 8-10 years old. Schedule in April or May while technicians have availability and before summer surge pricing kicks in.
If you’re thinking about replacing
Spring is also the best window to shop for a new AC or heat pump installation, for the same reason: contractors aren’t slammed, lead times are short, and you have time to compare bids thoughtfully rather than making a decision in 100°F heat.
The spread between bids is real and it’s not random. It’s usually SEER rating, electrical scope (a panel upgrade one contractor flags and another doesn’t), and warranty depth — not contractor margin. A low bid that skips the electrical panel assessment entirely is a red flag worth catching before you sign. BidSmart can help you compare your own quotes line by line. Getting bids in April or May lets you run that comparison without a July heat wave forcing the decision.
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Related: Best Thermostat Settings for Summer · AC Short Cycling: Causes and Fixes · Why Your AC Isn’t Cooling
For what a legitimate tune-up visit should cost and how to spot a sales call dressed as maintenance, see what an AC or furnace tune-up should cost.
