Few things are more annoying than an air conditioning (AC) unit that works overtime without actually cooling your living space. It’s also concerning for your utility bill. If your house feels like an oven even with the AC running, your system might be struggling with a hidden issue. Knowing how to troubleshoot the problem can help you restore your home’s comfort.
Common Culprits Keeping Your Home Uncomfortably Warm
Research shows that a household with AC consumes 36% more electricity on average than homes without. So, if your system is running all day just to blow lukewarm air, it’ll drive up your monthly bills and put severe wear and tear on your unit. Here are the typical culprits behind this problem.
Dirty Air Filters
The air filter traps dust, pollen, pet dander and other particles before they can enter your heating, ventilation, and air conditioning (HVAC) system’s internal workings. It gets clogged over time.
When it’s packed with dirt, the blower motor has to work harder to pull air through the system, which can cause your air conditioner to fail. The lack of airflow can even cause the evaporator coil to drop below freezing.
Poor Insulation and Hidden Air Leaks
Your home relies on insulation in the attic and walls to act as a thermal barrier. However, the insulation can settle, compress or degrade over time. Similarly, the caulk and weatherstripping around your exterior doors and windows can become dry and brittle as the house ages. When these seals fail, hot, humid air can seep inside as your conditioned air escapes.
In this scenario, your air conditioner is fighting a losing battle against a leaky house. It will run endlessly, trying to cool down a space that cannot retain cold air.
Problematic Thermostat Placement
A thermostat that’s in direct sunlight, near a heat-generating appliance or tucked in a drafty hallway may get false readings. It may think the room is much warmer or cooler than the rest of the house. The AC will then work overtime to cool a room that’s already comfortable, leaving the rest of your home hot and uncomfortable.
Beyond placement, how you interact with your thermostat matters. A common misconception is that it’s more efficient to turn the AC off when you’re leaving for the day. In reality, letting your home get hot forces the system to work harder later to restore comfort, which can also increase indoor humidity.
Low Refrigerant Levels
Refrigerant carries heat from inside your home to the outside by continuously cycling between the indoor and outdoor units. If its levels are too low, there might be a leak somewhere in your system.
Your system absorbs and releases heat less efficiently when it runs low on refrigerant. As a result, the evaporator coil loses pressure and may even freeze over. Your AC will continue blowing warm or barely cool air while your home remains uncomfortably hot.
Damaged or Disconnected Ductwork
Your ductwork is the hidden highway that delivers cold air from the blower motor into your rooms. In many homes, especially older ones, these ducts run through the hottest areas of the house, like attics, crawlspaces and exterior walls. Over time, ducts can develop leaks, cracks or disconnected joints.
When there’s a leak in your attic ductwork, the chilled air escapes into the rafters before it reaches your living room. Even if your AC runs perfectly, your vents will have weak airflow if cold air leaks into unoccupied spaces, keeping your home stubbornly warm.
An Undersized Cooling System
If your AC is too small for your home's square footage, or if you’ve recently added an extension or sunroom, it may not remove heat fast enough.
During peak afternoon heat, an undersized unit will run continuously at full output. Because it can never catch up to the heat gain, the thermostat will never reach its setpoint until late at night. In short, the system cannot keep up with your home’s demand, resulting in long, ineffective run cycles.
Tips for Improving Your Air Conditioner’s Cooling Efficiency
While issues like refrigerant leaks require a licensed professional, you can make several adjustments today to reduce your home’s heat load and give your AC a break.
