AC Running Nonstop in a Heat Wave? Here’s What’s Normal and What’s Not

When a New Hampshire heat wave hits, your air conditioner may run for hours without much of a break.

That can make homeowners wonder:

Is my AC broken, or is it just really hot outside?

The answer depends on what your system is doing.

Sometimes, an AC that runs nonstop during extreme heat is doing exactly what it is supposed to do. Other times, the heat wave is revealing a problem that needs service.

Here’s how to tell the difference.

First, Know This: Your AC Has Limits

Your air conditioner is designed to keep your home comfortable during normal summer weather.

But during extreme heat, especially in the hottest part of the afternoon, your home may gain heat faster than your AC can remove it.

That means your system may:

• Run almost nonstop
• Struggle to reach the thermostat setting
• Let the indoor temperature rise a few degrees
• Catch up later in the evening when outdoor temperatures drop

That does not always mean something is wrong.

If your thermostat is set to 72 and the house climbs to 75 or 76 during a major heat wave, your system may simply be working at full capacity.

What Is Normal During a Heat Wave?

Your AC may be operating normally if:

• The system runs for long stretches
• Cool air is still coming from the vents
• Airflow feels normal
• The indoor temperature is only a few degrees above the thermostat setting
• The house starts cooling down again in the evening
• There are no unusual noises, smells, or electrical issues

In this case, your system may just need a little help reducing the heat load inside the home.

What You Can Do Before Calling for Service

Before assuming your AC is broken, try these simple steps.

1. Check the Air Filter

A dirty filter can block airflow and make your AC work much harder.

If the filter looks dusty or clogged, replace it.

This is one of the easiest ways to help your system breathe better during hot weather.

2. Keep Vents and Returns Open

Walk through the house and make sure:

• Supply vents are open
• Return vents are not blocked
• Furniture, rugs, curtains, or laundry baskets are not covering airflow

Blocked airflow can make rooms warmer and increase strain on the system.

3. Close Blinds During Direct Sun

Sunlight through windows can heat up a room quickly.

During the hottest part of the day, close blinds or curtains on sunny sides of the house.

This can make a noticeable difference, especially in upstairs bedrooms and rooms with large windows.

4. Avoid Dropping the Thermostat Too Low

Lowering the thermostat to 65 will not make your AC cool faster.

If the system is already running, it is already doing all it can.

Setting the thermostat extremely low only makes the system run longer and harder.

During extreme heat, a setting around 76 to 78 can help reduce stress while still keeping the home comfortable.

5. Check the Outdoor Unit

Your outdoor AC unit needs room to release heat.

Make sure the area around it is clear of:

• Tall grass
• Leaves
• Weeds
• Mulch buildup
• Shrubs
• Grass clippings

Try to keep at least 2 feet of open space around the unit.

If the coil looks covered in pollen, dirt, or grass clippings, it may need cleaning.

When You Should Call Al Terry

Some signs point to a real AC problem.

Call for service if you notice:

• Warm air coming from the vents
• Weak airflow
• Ice on the indoor coil or refrigerant lines
• The outdoor unit is not running
• The system turns on and off repeatedly
• The breaker trips
• The house does not cool down even after sunset
• The indoor temperature keeps climbing
• You hear buzzing, grinding, rattling, or loud humming
• You notice a burning smell

These symptoms are not just “normal heat wave behavior.” They may point to an issue like restricted airflow, a dirty coil, low refrigerant, a failing capacitor, or an electrical problem.

Why Heat Waves Bring Out AC Problems

An AC system may seem fine during mild weather, then suddenly struggle when the first big heat wave arrives.

That happens because extreme heat puts extra stress on every part of the system.

Problems that were small before can become obvious, including:

• Dirty filters
• Dirty outdoor coils
• Weak fan motors
• Low refrigerant
• Aging capacitors
• Ductwork leaks
• Poor airflow
• Electrical issues

In other words, the heat wave may not be the cause of the problem. It may simply be the moment you finally notice it.

Should You Get a Bigger AC?

Not always.

A bigger air conditioner is not automatically better. If a system is too large for the home, it may cool the air quickly but fail to remove enough humidity.

That can leave your home feeling cold, damp, and uncomfortable.

The better answer is to find out why the system is struggling.

It may need:

• Basic maintenance
• A cleaner outdoor coil
• Better airflow
• Duct repair
• A new capacitor
• Refrigerant leak repair
• Better insulation
• A properly sized replacement system

A professional inspection can help separate a simple repair from a larger comfort issue.

The Simple Rule for Homeowners

During a heat wave, ask yourself these three questions:

1. Is cool air coming from the vents?
2. Is airflow normal?
3. Does the house start cooling down after the outdoor temperature drops?

If the answer is yes, your AC may just be working hard in extreme conditions.

But if you have warm air, weak airflow, ice, strange noises, electrical issues, or temperatures that keep climbing, it is time to schedule service.

Need Help With an AC That Can’t Keep Up?

If your air conditioner is running nonstop and your home still feels uncomfortable, Al Terry Plumbing, Heating & AC can help determine what is really going on.

Sometimes the fix is simple. Sometimes the system needs a deeper look.

Either way, getting the right diagnosis can help you stay comfortable, protect your equipment, and avoid a breakdown during the next stretch of hot weather.