Preparing Your AC for Summer

The first hot day of summer is the wrong time to discover your air conditioner doesn't work. By then, every HVAC company in town is booked solid, and you're sweating while you wait.

A little spring prep work prevents that scenario. Your AC has been sitting idle for months—exposed to weather, possibly home to critters, and definitely covered in debris. Take an hour in late April or May to get it ready, and you'll have cool, worry-free summer ahead.

The 24-Hour Rule#

Before we get into the prep checklist, there's one critical rule you need to know.

Here's why: Your air conditioner has a compressor that contains oil. When the system sits idle, that oil settles to the bottom. The compressor also has a small crankcase heater that keeps the oil warm and properly distributed.

When you turn on the breaker, you're activating that heater. Give it 24 hours to warm the oil before you actually run the AC. Starting the compressor with cold, settled oil can cause serious damage.

Mark your calendar: turn on the breaker one day, run the AC the next.

Outdoor Unit Prep#

The outdoor unit (condenser) does the hard work of dumping heat from your home into the outside air. It needs clear airflow to work efficiently.

Remove Covers and Check for Damage#

If you covered your AC for winter, remove the cover completely. Never run the system with any kind of cover in place—even a partial cover restricts airflow and can cause the compressor to overheat.

While you're there, look for obvious damage: bent fins, damaged wiring, rust, or signs that animals have been nesting inside. Mice love to chew wires, and their damage isn't always obvious from the outside.

Clear Debris#

Leaves, twigs, grass clippings, and dirt accumulate around and inside the outdoor unit. Clear everything away from the unit itself, and trim back any vegetation to maintain at least two feet of clearance on all sides.

This clearance isn't arbitrary—restricted airflow can reduce your AC's efficiency by up to 30%. That's higher energy bills and a system that struggles on the hottest days.

Clean the Coils#

The condenser coils (the fins on the outside of the unit) need to be reasonably clean to transfer heat effectively.

Use a garden hose with a gentle spray setting—never a pressure washer, which can damage the delicate fins. Spray from the inside out to push debris away from the unit rather than further into it. Work your way around the entire unit.

For heavily soiled coils, you can use a foaming coil cleaner (available at hardware stores). Spray it on, let it sit for 10-15 minutes, then rinse thoroughly.

Straighten Bent Fins#

If you notice bent fins on the condenser, you can straighten them with a fin comb (a cheap tool available at hardware stores). Bent fins restrict airflow, so it's worth taking a few minutes to fix them.

Indoor Prep#

The outdoor unit gets most of the attention, but don't neglect the indoor components.

Replace the Air Filter#

Start the cooling season with a fresh filter. This is especially important if you ran your heating system all winter—that filter has been working hard and is probably ready for replacement.

Clear the Condensate Drain#

Your AC removes humidity from the air, and that moisture has to go somewhere. It drips into a drain pan and exits through a condensate drain line. Over the off-season, algae and mold can grow in this line, causing clogs.

Pour a quarter cup of white vinegar into the drain line access point (usually a T-shaped vent near the indoor unit). This kills algae and helps prevent clogs. Do this monthly during cooling season.

Check the Refrigerant Lines#

Look at the copper pipes running between your indoor and outdoor units. The larger pipe (the suction line) should be covered with foam insulation. Check that this insulation is intact with no gaps, cracks, or deterioration.

Damaged insulation reduces efficiency and can cause condensation problems. It's inexpensive to replace if needed.

Testing Your System#

With prep work done and 24 hours elapsed since you turned on the breaker, it's time to test.

The Test Run#

1. Set your thermostat to cooling mode with the fan on "auto"
2. Set the temperature 4-5 degrees below the current room temperature
3. The outdoor unit should start within 30 seconds to a minute
4. You should feel air blowing from the top of the outdoor unit—it will be warm/hot, which is normal (that's the heat being removed from your home)
5. After a few minutes, check the large copper pipe (suction line) at the outdoor unit—it should feel cold
6. Check vents inside for cool airflow
7. Let the system run for at least 15 minutes

What You're Looking For#

Good signs:

• Outdoor unit starts promptly
• Outdoor fan spins freely
• Hot air blowing from top of outdoor unit
• Cold suction line after a few minutes
• Cool air from indoor vents
• System runs steadily without cycling on and off

Warning signs:

• Outdoor unit doesn't start
• Strange sounds (grinding, squealing, hissing)
• Ice forming on the refrigerant lines or outdoor unit
• No cool air after 15 minutes
• System cycles on and off rapidly
• Burning or electrical smell

If you notice any warning signs, turn off the system and call for professional service before the summer rush.

When to Skip DIY and Call a Pro#

Schedule professional AC maintenance if:

• It's been more than two years since a professional tune-up
• Your system is 10+ years old
• You noticed any warning signs during testing
• Your energy bills were unusually high last summer
• The system struggled to keep up on hot days last year

A professional tune-up typically costs $75-150 and includes checking refrigerant levels, cleaning coils more thoroughly than you can with a hose, testing electrical components, and verifying the system operates within specifications.

The Cover Debate#

Should you cover your AC for winter? Most HVAC professionals actually say no.

Outdoor AC units are built to withstand weather. Full covers trap moisture inside, promoting rust and corrosion. They also provide shelter for mice and other pests.

If you have a specific problem—like a tree that drops debris directly onto the unit—use a top-only cover (a piece of plywood works fine). Never wrap the entire unit. And whatever you do, never forget to remove the cover before running the system.

Spring Checklist#

One day before first use:

• Turn on outdoor unit circuit breaker (24-hour rule)

Day of first use:

• Remove any covers
• Clear debris from around unit
• Trim vegetation back 2+ feet
• Rinse coils with garden hose
• Replace indoor air filter
• Pour vinegar down condensate drain
• Check refrigerant line insulation
• Run test cycle for 15+ minutes
• Verify cool air from vents