Why Is My AC Not Cooling? Common Air Conditioner Issues & Fixes

When your AC stops cooling in the middle of a hot Northern Virginia summer, you most likely want to figure out what’s wrong and fix it ASAP. Whether you live in Fairfax, Reston, Herndon, Sterling, or nearby, a malfunctioning air conditioner can quickly turn into a major disruption.

Summer is peak season for AC repair, and while some issues are easy to fix, others require the attention of a licensed HVAC technician. This guide will help you understand the most common AC problems, what you can check yourself, and when it’s time to call a pro.

Common Reasons Your Air Conditioner Isn’t Cooling

Several issues can cause your air conditioner to stop cooling effectively. Here are some of the most common issues we see in homes across Northern Virginia.

Dirty or Clogged Air Filter

A dirty air filter is one of the simplest and most frequent causes of poor cooling. When the filter is clogged with dust or debris, airflow becomes restricted, making it harder for your system to circulate cold air. This can lead to uneven cooling or even a frozen evaporator coil.

Low Refrigerant Levels

Refrigerant is the chemical that absorbs heat from your home and releases it outside. If your system is low on refrigerant, you might notice warm air blowing from your vents or ice forming on the coils.

Low refrigerant usually means there’s a leak, and DIY refilling is never recommended — it requires proper tools, training, and EPA certification. A professional technician can locate the leak, make the necessary repairs, and safely recharge the system.

Thermostat Settings or Malfunctions

Sometimes, the issue isn’t the AC itself — it’s the thermostat. Your thermostat may be set to “heat,” the temperature might be set too high, or the fan might be set to “on” instead of “auto.” In other cases, faulty sensors or wiring can prevent the thermostat from communicating properly with your system.

Frozen Evaporator Coils

If you notice ice buildup on the indoor unit or poor airflow from your vents, frozen evaporator coils could be the cause. This problem often stems from restricted airflow — typically due to a dirty filter or blocked ducts — or from low refrigerant levels.

Electrical or Circuit Issues

Your AC relies on many electrical components to function correctly. If your unit won’t turn on at all, a tripped circuit breaker or blown fuse could be to blame. Faulty wiring or connections can also cause intermittent power loss, preventing your system from running properly.

Problems With the Outdoor Unit

The outdoor unit houses key components like the compressor and condenser coil, which are essential for heat exchange. If this unit becomes clogged with leaves, dirt, or other debris, it can’t expel heat efficiently. Signs of trouble include reduced cooling performance, strange noises, or the fan not running.

What You Can Check Yourself Before Calling for AC Repair

Before scheduling a service, take a few minutes to perform these simple checks:

• Check the air filter and change it if needed.
• Make sure the thermostat is set to “cool” and the correct temperature.
• Check your circuit breaker to see if a breaker has tripped.
• Check the outdoor unit’s clearance.
• Look and listen for obvious signs (ice, buzzing, no airflow).

When To Call a Professional for AC Repair

Beyond basic troubleshooting, HVAC repair is not a DIY job. Trust a trained technician to diagnose the problem correctly and safely make effective, lasting repairs. If you notice any of the signs below, don’t wait — call a licensed HVAC technician for AC repair:

• Cooling issues that don’t resolve after basic troubleshooting
• Leaking refrigerant or iced-over coils
• An AC that runs constantly or short-cycles
• Strange noises, burning smells, or water leaks

Schedule an Expert AC Repair in Northern Virginia

From minor cooling issues to complete system failures, John Nugent & Sons is your go-to resource for expert AC services. For over 50 years, our local, family-owned company has delivered quality service to homeowners throughout Northern Virginia.

Our licensed technicians handle both seasonal and emergency AC repairs with the honesty, speed, and professionalism we’re known for. From Fairfax to Reston, Herndon, Sterling, and beyond, we’re ready to restore your comfort.

Contact our team to schedule your AC repair in Northern Virginia today.