Why Is My Air Conditioner Not Cooling?

When It’s Not So Cool

Air conditioner not cooling? The air conditioner is seemingly on, but the house is still hot. What’s the problem? 

There are all sorts of reasons why your air conditioning system may not be cooling. Let’s take a look first at how your air conditioner works, and then what to check to determine why the air conditioner is not cooling. The steps to cover include checking the following:

• Thermostat
• Circuit breaker
• Disconnect box
• Filter
• Obstructions

More serious issues require a professional air conditioning technician to see why the air conditioner is not cooling, including checking:

• Evaporator coil
• Fan motor
• Line Voltage
• Compressor
• Condenser coil
• Capacitor
• Contactor
• Condenser fan motor
• Outdoor disconnect
• Refrigerant

How an Air Conditioner Works

An air conditioner draws in warm air that passes through a filter and is then blown over an evaporator coil that contains refrigerant to pull heat out of the air. As the refrigerant absorbs heat from the air, it transforms from liquid to gas form. The cooled air is blown back into the house.

The gaseous refrigerant is conveyed to the compressor located in the outside unit. The compressor increases the temperature of the refrigerant so it becomes a super hot vapor. From there, the refrigerant passes to the condenser which removes the heat from the refrigerant into the outside air. The cooled refrigerant is again liquified, and repeats the cycle.

AC Not Working? 

If the air conditioner is not cooling, there are a few things the average homeowner can look at to possibly correct the problem. 

• Check the thermostat(s). It may seem too obvious, but sometimes the wrong buttons get pressed. Make sure the thermostat is set to cool and the desired temperature is set lower than the actual temperature of the room. If that doesn’t appear to solve why the air conditioner is not cooling, change the batteries (not all thermostats have batteries, so consult the user manual). If the display is flashing or doesn’t respond to how you try to program it, it is possible the thermostat is malfunctioning and requires replacement. This probably requires a technician to install.

• Check the circuit breaker. Typically, there are separate breakers for the indoor and outdoor air conditioning units. Even if you don’t see the breakers in the tripped or off position, flip them on and off and see if they remain on. Electrical surges cause the breakers to trip; that’s what they are there for, to prevent the surge from damaging equipment. If the circuit breaker remains tripped, it’s been damaged and requires replacement.

• Check the disconnect box. Located on the outside unit, the disconnect box serves a similar function as a circuit breaker. If the disconnect is set to off, turn it back on. But don’t walk away just yet. Examine the wired connections in the box to make sure nothing is frayed or, more seriously, burning. If so, the disconnect most likely goes back to the off position and the box requires rewiring.

• Clear obstructions. Objects and debris around air conditioning unit vents restrict airflow. If present, remove them. 

• Check/change the filter. A dirty filter impedes airflow and inhibits heat transfer. The air filter is usually checked or changed with regular maintenance, but don’t rule it out. And especially don’t rule it out if you haven’t performed regular maintenance.

When You Need a Professional AC Diagnosis

If you’ve done all of the above and the air conditioner is still not cooling, you probably need to call an AC technician. While if you are handy you could try further troubleshooting on your own, for the average homeowner this isn’t a DIY project. A trained HVAC professional can properly diagnose and repair any malfunctioning part of your air conditioner system that is causing it not to cool properly.

Potential sources of cooling problems are:

• Dirty or broken evaporator coil. A dirty or moldy evaporator coil results in poor heat transfer from the air to the refrigerant. In many cases cleaning the coil corrects the problem; however in some cases a replacement coil is necessary.
• Bad or dirty fan motor. The fan pulls air to cool your home. Proper cleaning ensures the fan can pull enough air to sufficiently provide cooling. A malfunctioning fan motor requires replacement.

• Bad high voltage wire. This wire signals the air condenser to turn on. A loose, damaged, or otherwise faulty wire does not allow the air condenser to turn on.

• Bad compressor. The compressor pressurizes the refrigerant and pushes it through the air conditioner  system. If the compressor malfunctions, the air conditioner is not cooling because the system can’t remove heat from the air.

• Outside condenser. A dirty condenser coil can’t perform proper heat transfer. Cleaning fixes the problem in most cases, but sometimes the condenser fails and requires replacement.

• Broken capacitor. The outside air conditioning unit won’t start if the capacitor malfunctions. It requires replacement.

• Bad contactor. The contactor allows electricity to flow to the compressor and outdoor fan motors; in essence, it is the device that turns on the air conditioner. The contactor can corrode over time, preventing the condenser unit from starting, and the air conditioner is not cooling.
• Faulty condenser fan motor. The condenser fan converts heated refrigerant from a gas back to a liquid by blowing air past the condenser coils. If the condenser fan motor isn’t working properly, the air conditioner is not cooling.
• Low refrigerant. This is literally the lifeblood of your air conditioning system. If the refrigerant is low, it is less pressurized, which impairs heat transfer. However, while low refrigerant is not an uncommon cause for air conditioning not cooling, it is a symptom of a larger issue. Refrigerant gets low because there is a leak somewhere. So you can top off the refrigerant, but it is only going to leak out again. An HVAC technician can test the system and locate the source of the leak.

Prevention is the Best Medicine

Over time, things break down. Sometimes a quick cleaning is the fix; sometimes parts need to be replaced; sometimes things get complicated. One way to head off the possibility of your air conditioning not cooling just when you need it in the middle of a heat wave is to perform regular HVAC maintenance. This not only helps avoid an uncomfortable situation, it also ensures your air conditioning system is running properly at optimum efficiency and extends its useful lifespan.

We can’t emphasize enough that the reason for the adage “prevention is the best medicine” is because it is true. It actually costs less to pay for a regular air conditioning tune-up than it does to make repairs when components fail because they weren’t properly maintained. Regularly maintained HVAC systems enjoy longer lifespans. In addition, the cost of a maintenance plan becomes part of your regular home budget accounting, letting you avoid surprise expenses from unforeseen and likely costly repair bills. 

Ongaro & Sons—Your Air Conditioning Experts 

Ongaro & Sons licensed and experienced HVAC professionals perform air conditioning repair and maintenance service, always to your complete satisfaction, always at an affordable cost consistent with industry standards. With over 90 years of experience providing high-quality services, Ongaro & Sons is a licensed state contractor with fully insured, qualified, and professional technicians. Our 100% guarantee ensures your complete satisfaction. 

Contact Ongaro & Sons or call us at 707-419-3135 today if you need emergency system repair because your air conditioner is not cooling. Let’s discuss a regular maintenance plan to avoid any costly emergency problems. We look forward to discussing your needs, and to providing the service that keeps you comfortable and prevents you getting hot under the collar.