Why Is Your Air Conditioning Not Working? 8 Common Causes
The summer heat can feel unbearable when your air conditioner is on the fritz. The moment cold air stops blowing from the vents on a hot and humid August afternoon in any part of Los Angeles often leads to an immediate eye-widening, “Oh no, the AC is not working!”
Whether you’re at home or at work, anyspace with a faulty AC unit needs fixing ASAP. Doing a quick Google search for, “Why is my air conditioning not working?” could give you some results, but it may not be comprehensive or detailed enough. From checking power switches and thermostat settings or flipping a tripped breaker, there are several DIY remedies you can try before calling in the HVAC experts. Still and all, don’t hesitate to do just that if you want quick service, DIY is not recommended. Minor issues could become major without the right guidance. So whether you’re just mildly concerned about why your AC unit isn’t working or need immediate help, having a good on hand is always a good idea.
In the meantime, here are some of the top causes as to why your air conditioner may not be working – and what to do about it.
Reason 1: Thermostat Settings Causing Air Conditioning System Failure Issues
Thermostat screens sometimes go blank because the internal batteries die after months or years of constant daily use. This simple power loss prevents the cooling system from receiving the signal to start its cycle. Setting the device to heat instead of cool also stops the cold air from flowing. Check the display for a low battery icon or incorrect temperature settings before calling for help. Fresh batteries often restore the connection between the wall unit and the outdoor condenser unit instantly.
Incorrect fan settings can cause the system to blow warm air even when the compressor stays off. Switching the fan from on to auto forces the unit to blow air only during cooling cycles. This adjustment keeps the indoor humidity low and prevents the house from feeling sticky during the day. Most modern thermostats require a specific cooling mode to activate the refrigerant lines and the fans. Verify that the temperature setting stays at least five degrees below the current room heat.
Reason 2: Dirty Air Filters Restrict Airflow and Cooling Performance
Thick layers of dust and debris may block the air from passing through the mesh filter. This buildup forces the motor to work much harder while moving very little cool air indoors. Restricted airflow often leads to frozen evaporator coils because the cold refrigerant cannot release its icy chill. Changing the filter every 1-3 months keeps the air moving freely and prevents the motor from burning out. Look for a clean white surface on the filter to confirm it works correctly.
Clogged filters also lower the air quality inside the home by spreading allergens through every room. The air conditioner struggles to reach the target temperature when the intake vents remain covered in grime.
Improving the airflow helps the air conditioner cool the entire house much faster during heat waves.
Reason 3: Tripped Circuit Breakers Cutting Power to AC Units
Electrical surges during heavy storms often flip the safety switches inside the main breaker panel. This sudden loss of electricity stops the outdoor condenser from spinning or cooling the warm indoor air. Locating the specific switch labeled for the air conditioner helps identify a potential power supply failure. Flip the switch completely to the off position before pushing it back to the on side. Resetting the breaker usually sends power back to the unit and starts the cooling process again.
Constant tripping indicates a serious electrical problem that requires a professional inspection of the wiring. The air conditioner draws too much current when the internal parts begin to wear out or fail. Overloaded circuits heat up quickly and trigger the safety mechanism to prevent a dangerous house fire. Avoid turning the breaker back on if it trips a second time after the first reset. Leaving the power off protects the expensive internal components from permanent damage during a major electrical fault.
Reason 4: Low Refrigerant Levels Reducing Cooling Capacity and Efficiency
Refrigerant acts as the heat carrier that moves warmth from inside the house to the outside. Tiny holes in the copper lines allow this vital fluid to leak out over several months. Low levels prevent the system from absorbing enough heat to cool the rooms down to a comfortable temperature. The result? The air conditioner runs for hours without stopping while the house stays warm and very uncomfortable. Only a certified HVAC technician can find the leaks and refill the system with the correct fluid.
One of the clear sign that your refrigerant may be leaking is if you notice ice forming on the copper pipes outside. The low pressure causes the temperature of the coils to drop below the freezing point of water. Moisture from the air turns into thick frost that blocks the heat exchange process entirely. Continuing to run the unit with low refrigerant ruins the compressor and leads to expensive repair bills. Shutting the system down immediately helps prevent the motor from burning out due to the high strain.
Reason 5: Frozen Evaporator Coils Blocking Proper Heat Transfer Process
Evaporator coils stay hidden behind a metal panel inside the indoor part of the air conditioner. These coils must stay clean to absorb the heat from the air passing through the metal fins. Thick layers of dust or low airflow cause the coils to get too cold and freeze. A solid block of ice prevents the air from moving through the vents and into the rooms. Turning the cooling mode off and running the fan helps melt the ice over several hours.
Dirty coils act like an insulating blanket that stops the refrigerant from doing its job. The system works harder and longer while failing to lower the temperature by even a few degrees. Regular cleaning prevents the buildup of grime that leads to these freezing issues during the summer. Check the condensate drain line for clogs because standing water also contributes to ice formation on the metal. Keeping the coils dry and clean helps the air conditioner run at peak performance every single day.
Reason 6: Faulty Capacitors Preventing Air Conditioning Startup and Operation
Capacitors act like large batteries that give the motors a powerful boost to start spinning quickly. These small cylindrical parts often fail during extreme heat or after years of heavy seasonal use. A clicking or humming sound from the outdoor unit usually points to a dead or dying capacitor. The fan or compressor cannot start without this extra jolt of electricity from the capacitor Replacing a bad capacitor remains one of the most common HVAC repair calls we get at C&M Mechanical Heating and Cooling.
Bulging tops or leaking fluid indicate that the capacitor has reached the end of its useful life. Heat causes the internal chemicals to expand and break the metal casing of the small part. The air conditioner will not turn on even if the thermostat sends a signal for cooling. Avoid touching these parts because they hold a dangerous electrical charge even when the power stays off. Installing a new capacitor restores the starting power and gets the cold air flowing through the house again.
Reason 7: Clogged Condensate Drains Triggering System Shutdowns and Leaks
Moisture from the air collects on the cold coils and drips into a plastic drain pan. A long PVC pipe carries this water outside the home to keep the indoor area dry. Algae and slime often grow inside the pipe and block the flow of water over time. The pan fills up quickly and triggers a safety float switch to shut the system down. This prevents a messy flood that could damage the floors or the ceiling of the house.
Cleaning the drain line with a vacuum or a brush removes the thick clogs easily. Water leaking from the base of the indoor unit indicates that the drain line has a blockage. Clear the path for the water to ensure the air conditioner continues to run without any interruptions. Regular checks on the drain line prevent water damage and keep the cooling system operating smoothly.
If you’d prefer not to DIY it, a solid and recommended alternative is to call a professional HVAC contractor. This ensures that the job will get done correctly and safely, leaving no room for wondering if you did it right.
Reason 8: Outdoor Condenser Issues Limiting Heat Release Efficiency Outdoors
The outdoor unit needs plenty of open space to release the heat collected from inside the house. Tall grass and thick bushes often block the metal fins and trap the hot air nearby. Sure, beautiful landscaping is nice but it shouldn’t compromise the performance of your HVAC unit. This restriction makes the compressor work much harder to cool the refrigerant back down for the next cycle. Clean the area around the metal box and remove any debris like leaves or dry twigs. Keeping a two foot gap around the unit allows for maximum airflow and better cooling.
Bent metal fins on the sides of the unit also prevent the air from moving correctly. Hail storms or stray rocks can also sometimes flatten these thin pieces and reduce the efficiency of the system. A special tool called a fin comb helps straighten the metal to restore the original air paths. Washing the coils with a gentle garden hose removes the dust and dirt that accumulates during the year. Clear coils help the air conditioner release heat faster and keep the indoor temperature very comfortable.
Call C&M Mechanical Heating and Cooling Today For Fast Local Air Conditioning Help
Hot days turn stressful fast when your cooling system fails, and fast action keeps damage from growing.
At C&M Mechanical Heating and Cooling, we respond quickly to air conditioner issues in Santa Clarita, CA. OOur team handles homes and businesses, focusing on accurate fixes, fair pricing, and clear solutions.
C&M Mechanical Heating and Cooling takes over 25 years of field skill and combines it with proven business leadership to give homeowners and business owners in the Santa Clarita Valley and San Fernando Valley the best service possible.
Local roots matter to us, so we show up prepared. Our team speaks both English and Spanish, maintains total professionalism, and treats every property with care.
Need support after the initial fix? We’ve got you covered. After we repair your unit, our plans move smoothly into for ongoing comfort. Maintenance reduces surprise breakdowns, lowers repair bills, and builds lasting care through scheduled visits. Call now to book a service, protect your equipment, and keep your cooling steady with a trusted local small business.