It’s a hot summer day in Rochester. You walk inside expecting cool relief, but something’s off—your air conditioner is running, but your home isn’t getting any cooler. Or worse, it’s not running at all. Before you reach for the phone and schedule an emergency HVAC repair, it’s worth taking a few minutes to run through a basic AC troubleshooting checklist.
Sometimes, what seems like a major issue is actually a simple fix. From a tripped breaker to a dirty air filter, small problems can lead to big discomfort—but you don’t always need professional help to resolve them. In this guide, we’ll walk you through the most common things to check when your AC isn’t working properly. This could save you time, money, and the frustration of an unnecessary service call.
Check the Thermostat Settings
The first and easiest place to start is your thermostat. It might sound obvious, but thermostat issues are one of the most common culprits when an AC system isn’t cooling correctly.
Make sure your thermostat is:
- Set to “Cool” mode (not “Heat” or “Fan Only”)
- Programmed to a temperature lower than the current room temperature
- Displaying normally with no low battery warning or blank screen
If your thermostat runs on batteries, replacing them might restore full functionality. Also, double-check that no one in the house has changed the settings accidentally. A few quick adjustments here could restore your comfort without needing a technician.
Inspect the Circuit Breaker
If your AC system isn’t turning on at all, the issue could be electrical. Head to your home’s breaker panel and look for a tripped breaker. Central air conditioners usually have two breakers—one for the indoor unit (air handler) and one for the outdoor unit (condenser).
If a breaker is tripped:
- Turn it all the way off
- Wait a few seconds
- Switch it back on
If it stays on and your system restarts, great. But if it trips again, don’t force it. Frequent breaker trips are a sign of a deeper electrical problem that needs professional attention. Avoid repeatedly resetting a tripped breaker to prevent further damage or safety risks.
Look at the Air Filter
A clogged or dirty air filter is one of the most common reasons for poor cooling performance or a complete system shutdown. When the filter gets blocked, it restricts airflow and puts unnecessary strain on the AC system.
Check the air filter and ask yourself:
- Is it covered in dust or gray in color?
- Has it been more than 1–3 months since you last replaced it?
- Does the system seem to be blowing weak air?
If so, replace the filter with a clean one immediately. Clean air filters are essential for both cooling performance and indoor air quality. If your system is freezing up or short-cycling, this simple fix could solve the problem.
Check the Outdoor Unit
Your outdoor condenser unit plays a vital role in heat exchange. If it’s dirty, blocked, or not running, your AC will struggle or shut down entirely.
Inspect the outdoor unit for:
- Debris like leaves, grass clippings, or overgrown plants
- Signs that the fan is not spinning
- Ice on the coil or refrigerant lines
- Unusual buzzing, clicking, or complete silence
Clear any debris away and make sure there’s at least two feet of open space around the unit for airflow. If you notice ice or the unit is completely unresponsive, it may be time to call a professional.
Inspect the Vents and Airflow
Sometimes, the AC system is working fine, but the cooled air isn’t reaching all parts of the home. Poor airflow can result from blocked vents, closed registers, or ductwork issues.
Walk through your home and:
- Make sure all supply and return vents are open
- Remove any furniture or rugs that may be obstructing airflow
- Check for noticeable airflow from each vent
If some rooms feel warmer than others, or airflow feels weak, there could be a blower motor problem or duct leak involved. While these usually require professional diagnosis, ruling out the obvious first can save time.
Examine the Condensate Drain Line
Air conditioners remove humidity from the air, and that moisture drains away through a condensate line. If the line gets clogged with algae, dirt, or debris, the system may shut down as a safety precaution to prevent water damage.
Signs of a clogged drain line include:
- Water pooling near the indoor unit
- A full or overflowing drain pan
- Musty odors near vents or the unit
If you’re comfortable doing so, you can try flushing the line with a small amount of distilled vinegar to break up minor clogs. If the water doesn’t drain after flushing, it’s time to schedule a service call.
Listen for Unusual Sounds
Your air conditioner can tell you a lot through the sounds it makes. A healthy system will have a consistent hum when running. When something’s wrong, you might hear odd noises like:
- Clicking: could signal a failing relay or electrical issue
- Buzzing: may indicate a loose part, failing motor, or electrical problem
- Grinding or screeching: could be a worn-out belt or motor bearing
- Silence: a dead unit may mean loss of power or internal failure
Take note of when the sounds occur—startup, during operation, or shutdown—as this helps HVAC technicians diagnose the problem more quickly.
Smell for Odors
Unusual smells from your AC system should never be ignored. They’re often the first sign of a deeper issue and can indicate anything from mold growth to electrical problems.
Common AC-related odors:
- Musty or damp smell: mold in the ductwork or drain line
- Burning smell: possible electrical short or overheating component
- Rotten odor: potentially a dead animal in the ducts or return vents
If you smell anything unusual, turn off the system immediately and call an HVAC professional. Lingering odors can affect indoor air quality and even pose health risks.
When to Call an HVAC Technician
After going through this AC troubleshooting checklist, you’ll likely have a better idea of what’s wrong—or at least rule out some common causes. While simple fixes like replacing a filter or adjusting the thermostat can be DIY-friendly, more complex issues require a trained eye.
Call a professional if:
- The breaker trips repeatedly
- The outdoor or indoor unit isn’t turning on
- There are refrigerant leaks or ice on the system
- The drain line is severely clogged
- You hear loud, unusual sounds during operation
- Odors persist despite cleaning or filter changes
Attempting to fix complex issues on your own can lead to further damage or void your system’s warranty. A licensed HVAC technician can quickly pinpoint the problem and recommend a cost-effective solution.
Use This AC Troubleshooting Checklist Before Picking Up the Phone
There’s nothing worse than being stuck in the heat with an air conditioner that’s not working. But before you assume the worst, take a few minutes to walk through this AC troubleshooting checklist. You might discover that the problem is simple and something you can fix on your own.
For everything else, Trident Heating & Cooling is here to help. Our experienced technicians serve homeowners across Rochester with fast, reliable air conditioning repair services. Whether your issue is electrical, mechanical, or somewhere in between, we’ll get your system back up and running in no time.
Don’t sweat it—use this checklist to save time, avoid unnecessary repair costs, and restore your comfort quickly. And when in doubt, give Trident a call. We’re just a phone call away.