Before you rush to crank up the cool air, it is worth giving your system a quick checkup or risk needing an unexpected HVAC service when you least expect it. After sitting idle all winter, your AC needs a little prep to get back in the game. Here’s what to do before flipping that switch, so your air conditioner runs smoothly, safely, and efficiently from day one.
Remove Covers Before You Turn On the AC
If you covered your AC unit, great, but how you did it matters even more. A breathable, waterproof cover (specifically made for AC units) that doesn’t trap moisture is key. Avoid using tarps or plastic sheets, which can encourage rust or mold. If you didn’t cover it, don’t stress. Modern units are built to handle winter. Just be sure to clear off any debris or leaves that may have gathered around it. If you did cover it, check for condensation damage underneath, especially if it wasn’t breathable.
Going forward, consider a simple plywood top cover to protect the fan from falling ice or debris while leaving airflow unobstructed on the sides.
Check the Outdoor Unit Before You Turn on the Air Conditioner
Before powering up your AC, give the outdoor condenser unit a once-over. Look for crushed fins or bent coils, chewed wires (mice and squirrels love warm spots), nests in or around the unit, leaves, sticks, or mulch clogging the base. Shine a flashlight into the grille, pests like to build nests in the corners. Pests aren’t just nesting in the cabinet, they may be inside your conduit lines, chewing low-voltage control wires. If you hear buzzing or smell something “off,” call a pro before touching anything.
Restore Power for Safe HVAC Start Up
If you flipped the switch on the AC’s exterior disconnect box or cut power at the breaker, good call. That prevents accidental startups on freezing days. To safely restore power, flip the switch back on at the disconnect box or breaker. Wait at least 30 minutes before starting the system (or even better, wait for 6-12 hours, or ideally overnight, before running the cooling). This gives the compressor’s internal heater time to warm the oil, avoiding a hard start that could damage the unit.
Replace Filter Before HVAC Start Up
For spring startup, start fresh. If you use a reusable filter, wash and completely dry it before reinstalling. Use this moment to set a recurring phone reminder to change the air filter during the season, so it never slips your mind again. Change them every 1-2 months during peak use. If you’re using a high-MERV filter (like MERV 13+), check airflow monthly; it may be too restrictive for older systems. Because even a too-clean filter can be bad if it’s too thick for your system. Look for signs like whistling vents or longer cooling cycles (signs of airflow issues).
Set Thermostat to Cool to Turn On AC
Don’t wait for the first 90-degree day to find out something’s wrong. Switch your thermostat to cooling mode, set it a few degrees below room temperature, and listen. Does the indoor unit click on? Does the outdoor unit start up? Is cold air blowing from the vents within a couple of minutes? Run it in cooling mode, then check the differential. You should feel a 15-20°F drop between return and supply vents. If it’s only 5-10°F? Something’s off.
Also, double-check that your thermostat is level (if it is older) and that it has fresh batteries if it is battery-powered. Is the fan setting on “auto” or “on”? “Auto” prevents humidity buildup and energy waste. Is your programmable schedule still relevant? Many people change work routines and forget to update them, wasting money daily. If your thermostat has a “calibrate” option and hasn’t been touched in years, it could be reading temperatures wrong by 3-5 degrees.
Test System When You Turn On the Air Conditioner
Let it run for 15-30 minutes and stand near supply vents, and make sure the air is cool and steady. Measure the temperature at both the return and the furthest supply vent. Walk outside and check for weird noises or short cycling. Monitor your energy usage during that time with a smart plug or energy app; a spike of 2x your normal usage could indicate low refrigerant or a dirty coil dragging down efficiency. If anything seems off (rattles, low airflow, odd smells), better to catch it now than during a heatwave. Watch for short cycling (starts/stops every few minutes).
Best Time to Turn On AC – DIY or Call a Pro?
Doing basic checks yourself is smart, but for the deep stuff like refrigerant levels, electrical inspections, and coil cleaning, spring maintenance by a pro is worth every penny. If you’ve never had a HVAC tune-up or it’s been over a year, now’s the perfect time. Plus, spring is usually cheaper and less crowded than peak summer. HVAC professionals can perform static pressure testing (shows if your ducts are strangling your airflow), superheat/subcool readings (reveal hidden refrigerant or coil issues), and duct inspection with a camera (uncovers leaks, mold, or rodent damage you’ll never see with the naked eye).
