Why is My AC Not Working? Common Problems and Easy Fixes
Few things are more frustrating than coming home on a hot Northwestern day, expecting a blast of cool relief, and instead being greeted by warm, stagnant air. When your air conditioner stops working—or isn’t cooling the way it should—it can quickly become a major headache.
The good news is that many AC issues are surprisingly simple to diagnose and fix. Before you call in the professionals like an authorized dealer from Carrier Northwest, here are some common reasons your AC might not be working—and a few easy fixes you can try on your own.
Why is My AC Not Working? Here are the AC issues we’ll cover:
Thermostat Settings Are Incorrect
Clogged Air Filter
Tripped Circuit Breaker
Refrigerant Is Low or Leaking
Dirty or Blocked Condenser Unit
Blocked or Closed Vents
Faulty Capacitor or Contactors
Thermostat Sensor Issues
Thermostat Settings Are Incorrect
It might sound obvious, but start with your thermostat. If it’s accidentally been set to “heat” instead of “cool,” or the temperature is set too high, your AC won’t do much to chill your Northwestern home. Sometimes, dead batteries or a glitchy thermostat can also throw things off.
Double-check that it’s set to “cool,” and try lowering the temperature a few degrees below the current room temp. If the display seems unresponsive or blank, swap in a fresh set of batteries and try again.
Clogged Air Filter
A dirty air filter can restrict airflow, reduce efficiency, and even cause your AC to shut down. It’s one of the most common reasons an AC unit underperforms, and fortunately, it’s one of the easiest things to fix.
Pull out your filter—usually found in the return air duct or inside the air handler—and take a look. If it’s gray and dusty, it’s definitely time for a replacement. Try to check your filter at least once a month during peak use and change it every one to three months, depending on your system and household environment.
Tripped Circuit Breaker
If your AC won’t turn on at all, head to your electrical panel. It’s possible the breaker that controls the AC system has tripped. This often happens after a power surge or if the system is working harder than usual.
Look for a breaker labeled “AC” or “HVAC.” If it’s in the middle or “off” position, flip it to “off” first, then back to “on.” If the breaker trips again shortly after, stop there—it could be a sign of a larger electrical issue, and it’s best to call a technician like an authorized dealer from Carrier Northwest.
Refrigerant Is Low or Leaking
Refrigerant is what your AC uses to cool the air. If the system is low on refrigerant—often due to a leak—you’ll likely notice warm air coming from the vents or ice forming on the indoor coil. You might also hear a faint hissing sound.
Unfortunately, refrigerant problems aren’t DIY territory. A licensed HVAC technician needs to diagnose the issue, repair any leaks, and recharge the system. If you suspect this is the problem, it’s best to get help sooner rather than later to avoid further damage.
Dirty or Blocked Condenser Unit
Your outdoor condenser unit plays a key role in releasing heat from your home. But over time, dirt, grass, leaves, and debris can build up around it, restricting airflow and making the whole system work harder.
With the power turned off, gently clear away debris around the unit and rinse off the fins with a garden hose. Avoid using a pressure washer, which can bend the delicate fins. Keeping a two-foot buffer zone around your unit—free from plants or objects—can make a big difference in performance.
Frozen Evaporator Coil
If your AC is running but not cooling, a frozen coil might be to blame. This can happen when airflow is restricted, or if there’s a refrigerant issue. You may notice your system struggling to cool, or see ice buildup near the indoor unit.
First, turn off the AC completely and let the coil thaw—this can take several hours. Then check the air filter and replace it if it’s dirty. If the coil freezes again, it’s time to call a Carrier Northwest dealer to inspect for low refrigerant or airflow problems deeper in the system.
Blocked or Closed Vents
It seems minor, but closed or blocked vents can cause uneven cooling or make it seem like your AC isn’t working at all. If a room feels unusually warm, check that the supply and return vents are open and unobstructed.
Sometimes furniture, rugs, or even kids’ toys can block airflow without you realizing it. A quick walkthrough of your home can often solve the mystery of a warm room.
Faulty Capacitor or Contactors
Capacitors and contactors are small electrical components that help your AC start and run. When they go bad, the system might not turn on, or it might short-cycle and shut off randomly.
These parts carry high voltage and should only be checked or replaced by a qualified HVAC technician. If your system is unresponsive and you’ve already ruled out the thermostat and breaker, this might be the next likely culprit.
Thermostat Sensor Issues
Inside your AC, there’s a small sensor that measures the temperature of the air near the evaporator coil. If this sensor is out of position or malfunctioning, the AC may behave unpredictably—turning on and off too frequently or not running long enough to cool your space.
You can gently adjust the sensor by bending the wire slightly to bring it closer to (but not touching) the coil. If that doesn’t help, it may need to be replaced.
When to Call a Professional
If you’ve tried the simple fixes and your AC still isn’t working—or if you hear strange noises, smell burning, or see signs of a leak—don’t wait. Contact a licensed HVAC technician within the Carrier Northwest network. Prompt service can prevent a small issue from turning into an expensive repair.
Prevent Future Problems
Preventative maintenance is your best defense against mid-summer AC breakdowns. Replace filters regularly, keep the outdoor unit clear, and schedule an annual service checkup before cooling season begins. A little attention throughout the year can extend the life of your system and keep your Northwestern home comfortable when you need it most.
Reach Out Today for Professional Assistance
An air conditioner that isn’t working can be stressful, especially during a heat wave. But with a little troubleshooting, many common problems are easy to fix. Start with the basics—check your thermostat, filters, breaker, and outdoor unit. If you’re still stuck, don’t hesitate to call in a pro. It’s better to resolve the issue early than to risk a larger breakdown later on.
Got questions about your AC or want to schedule a seasonal tune-up? Reach out to an authorized dealer within the Carrier Northwest network—search for one today using our Find a Dealer page.