Why Your Air Conditioner Blows Air but Doesn’t Cool — and How to Fix It

An air conditioner is an essential appliance during hot summer days. However, many people encounter a frustrating problem: the AC runs and blows air, yet the room doesn’t feel cool. Even when you set it to Cool Mode, lower the temperature, and turn the fan to its highest level, the air may still feel warm and stuffy.

Why Does This Happen?

According to distributors and experienced technicians, the most common reason your air conditioner is running but not cooling properly is a dirty air filter. Over time, dust and debris accumulate on the filter, blocking airflow between the unit and your living space. This buildup restricts cool air from circulating effectively, reducing overall cooling performance.

A repair shop owner on Luong The Vinh Street (Hanoi) shared that around 70% of the air conditioners his team checks for poor cooling are found to have dirty indoor or outdoor coils. When both the indoor and outdoor units are covered with dirt, the AC must work much harder to maintain the desired temperature. This not only increases power consumption but also creates loud, unpleasant noises.

The Hidden Cost of a Dirty Filter

Home appliance experts point out that even a small amount of dust buildup can significantly affect your AC’s efficiency. Research shows that an air conditioner’s performance may decrease by 1% each week if the air filter isn’t cleaned. Over time, a clogged filter can reduce airflow, slow cooling, and increase energy use by 5–15% compared to a clean system. In the long run, this can lead to higher electricity bills and shorten the unit’s lifespan.

When to Clean Your AC Filter

If your air conditioner isn’t cooling as effectively as before or makes strange noises, the first thing to check is the air filter. You can easily remove and clean it after a period of use.

Technicians recommend cleaning household AC filters every 3–4 months if used daily. For systems used less frequently, every 6 months may be sufficient.

In commercial settings such as offices, restaurants, or factories, filters should be cleaned once a month due to higher operating hours and dustier environments.

How to Clean Your Air Conditioner Filter

Most of the dust in an air conditioner collects on the air filter, aluminum fins, and air vents inside the indoor unit. For the outdoor unit, dirt often gathers around the fan blades and inner corners.

Cleaning can be done at different levels, depending on how long it’s been since the last maintenance. If your air conditioner hasn’t been serviced in a long time, it’s best to call a professional technician. They will use specialized tools—such as a high-pressure water sprayer—to clean the coils, aluminum fins, and other internal components thoroughly.

However, if you maintain your AC regularly, you can clean the filters yourself by following these simple steps:

Step-by-Step Cleaning Guide

Step 1: Turn off the power completely. Unplug the unit or switch off the circuit breaker to ensure safety before you begin.

Step 2: Open the front panel of the indoor unit and carefully remove the air filter. Most indoor units have two removable filters.

Step 3: Clean the filter with water and a soft brush. Avoid using harsh detergents or scrubbing too hard, as this could damage the mesh.

Step 4: Dry the filter. Wipe it gently with a clean cloth and let it air dry completely before reinstalling. You can also use a dry cloth or brush to remove dust from other accessible parts of the indoor unit.

Step 5: Reinstall the filter and close the front panel securely.

Once everything is reassembled, turn the air conditioner back on and test its cooling. If the air still feels warm or there’s little airflow, it may indicate a deeper issue, such as refrigerant leakage, malfunctioning compressor, or blocked coils. In that case, contact a professional service provider for inspection and repair.

Additional Maintenance Tips

• Use a protective cover for your outdoor unit if it’s exposed to rain or direct sunlight.

• Avoid setting the temperature too low (below 22°C or 72°F) for long periods — it strains the system and consumes more energy.

• Keep doors and windows closed while the AC is running to prevent cool air from escaping.

• Schedule a full professional maintenance at least once a year before summer begins. This ensures your system operates efficiently and prevents unexpected breakdowns.

By maintaining a clean air filter and following regular cleaning routines, your air conditioner will not only cool faster and save electricity but also provide a more comfortable and healthy living environment all summer long.