Heat Wave Prep for Your AC or Heat Pump

Quick answer

To get your cooling ready for a heat wave, test it early, change a dirty filter, clear space around the outdoor unit, and open all vents. During the heat, close blinds on sunny windows and keep the thermostat steady instead of making big swings. If it stops cooling, run the safe checks, then call.

Key facts

When to test	Before the first hot stretch, not during it
Filter	Check monthly in heavy-use months (ENERGY STAR)
Outdoor unit	Keep weeds, debris, and stored items away
Thermostat	Steady setting; avoid big swings in extreme heat
If it stops	Thermostat, breaker (once), filter, drain switch, then call
Home too hot?	Go somewhere cooler

How do you get your AC ready before a heat wave?

Test it early, on the first warm day, not the first hot one. If something is wrong, you want to find out while you still have time. ENERGY STAR suggests having the cooling system checked by a contractor each spring.

Here are 6 checks you can do yourself:

1Set the thermostat to Cool and a few degrees below room temperature. Let it run and feel for cool air at the vents.
2Check the filter. Change it if it looks dirty.
3Clear leaves, weeds, and stored items away from the outdoor unit.
4Open supply vents in every room and make sure return grilles aren't blocked.
5Replace thermostat batteries if yours uses them.
6Look at the condensate drain line or float switch near the indoor unit for standing water.

Why does the outdoor unit need clear space?

The outdoor unit pushes your home's heat outside, and it needs open air to do that. When plants, fences, or stored items crowd it, it has to work harder and cools less.

Clark Public Utilities advises keeping the area around the outdoor unit clear of weeds and anything that could block airflow. Trim back plants. Move bikes, bins, and covers away. Don't stack anything on top.

Coil cleaning is a different job. ENERGY STAR lists cleaning the indoor and outdoor coils as part of a contractor check-up. Leave that, and anything behind a panel, for a technician.

Not sure what's wrong yet?

Start with the safe checks. Many problems are a setting, a breaker, or a filter.

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Why does the filter matter so much in hot weather?

A dirty filter chokes airflow right when your system needs it most. Less air across the indoor coil means less cooling. It can even lead to ice on the coil and the refrigerant lines.

ENERGY STAR says to check your filter every month, especially in heavy-use months like summer. Change it if it looks dirty, and at least every 3 months. Clark Public Utilities also advises keeping all registers fully open to keep airflow balanced.

What thermostat setting works during a heat wave?

Pick a comfortable setting and leave it steady. In extreme heat, your system may already be running close to flat out. If you let the house get very warm and then set it much lower, the system may not catch up until evening.

A few habits help:

Start cooling early in the day, before the house heats up.
Avoid big setbacks when you're away on the hottest days. A small one is fine.
Expect long run times on very hot afternoons. That can be normal.
The house may sit above your setting on the hottest afternoons, even when the system works fine.
A smart thermostat can help. ENERGY STAR notes many can learn your schedule and adjust while you're away.

Do closing blinds and shades really help?

Yes. Sunlight through windows heats a room fast, and your AC has to remove that heat. Blocking it before it gets in is one of the easiest things you can do.

Close blinds, shades, or curtains on windows that get direct sun, especially in the afternoon. Keep windows shut while it's hotter outside than inside. If it cools off at night, you can open windows then and close them again in the morning.

Put off heat-making chores, like using the oven or dryer, until evening. Fans help people feel cooler, but they don't cool the room. Turn them off when you leave.

What should you do if your AC stops working during a heat wave?

Start with the safe checks. Some shutdowns have a simple cause you can fix in minutes. If these don't solve it, stop and call.

1Check the thermostat: set to Cool, setpoint below room temperature, screen working.
2Check the breakers for the indoor and outdoor units. Reset a tripped breaker once. If it trips again, stop and leave it off.
3Make sure the power switch near the indoor unit is on. It often looks like a light switch.
4Check the filter. A clogged filter can shut down cooling.
5Look at the refrigerant lines at the outdoor unit. If you see ice, turn cooling off and call. Running it iced can make things worse.
6Check the condensate float switch or drain pan. If it's full of water, the system may have shut itself off. Call us.

If the home is getting dangerously hot, go somewhere cooler while you sort out the repair. Call 911 for a medical emergency.

When should you stop and call a technician?

Call when the safe checks don't fix it, or when you see or smell anything unusual. Leave electrical parts, refrigerant, and anything behind a panel to a technician.

The breaker trips again after one reset.
The outdoor unit hums but the fan doesn't spin.
You see ice on the lines or the indoor coil.
Water is leaking from the indoor unit.
You smell burning.
It runs but blows warm air.

Common questions

Should I turn my AC off when I leave during a heat wave?

Usually a small setback works better than turning it off. If the house gets very hot, the system may not catch up once you're home. A steady, modest setting is easier on the house and on you.

Why does my AC run nonstop in extreme heat?

On very hot days, long run times can be normal. The system is removing heat as fast as it can. If the air from the vents isn't cool, or the house keeps getting warmer, check the filter and look for ice, then call.

Can I hose off my outdoor AC unit?

Clearing leaves and debris around it is a safe homeowner task. ENERGY STAR lists coil cleaning as part of a contractor check-up, so leave deep cleaning for a tune-up. Never open the unit's panels.

Why are my AC lines frozen in summer?

Frozen lines usually mean low airflow or a refrigerant problem. A dirty filter or closed vents are common airflow causes. Turn cooling off, check the filter, and call. Refrigerant problems are technician-only.

Do fans cool down a room?

No. Fans move air over your skin, which helps you feel cooler, but they don't lower the room's temperature. Turn them off in empty rooms.

Should I get an AC tune-up before summer?

It's a good idea. ENERGY STAR suggests checking cooling in spring, because contractors get busy once summer arrives. A spring check can catch a weak part before the first heat wave.

What should I tell you when I call about an AC that stopped?

Tell us what it's doing and what you've already checked. Mention any ice, water, noise, or smell, and the system's age if you know it. That helps the tech come prepared.