Central AC Not Working? Here’s How to Troubleshoot Your AC Unit

Warmer weather is right around the corner in California, which means you’ll be running your air conditioner 24/7.

There’s no worse feeling than switching on your AC unit only to hear an awful sound — or no sound at all! Is your central AC not working?

Before you call in the professionals, there are a few troubleshooting tricks you can try (beyond changing the filter or hitting it with a random household object).

Keep reading to learn tips and tricks for troubleshooting your AC unit so you can enjoy a cool and comfortable summer.

The Problem and the Solution

When it comes to AC troubleshooting, the good news is that there are a few common culprits. Knowing the reasons why your central AC isn’t working can help you get to the bottom of the issue.

It Won’t Turn On

This is one of the most basic AC problems — it just won’t turn on. You flip the switch and instead of being met with cool, refreshing air, you feel nothing.

The issue is usually a lack of power. Check your breaker box for a blown breaker or tripped fuse. You may be able to fix this AC issue with the flip of a switch.

If that doesn’t do the trick, check the wiring in your thermostat. A loose or frayed wire could also prevent your unit from turning on.

Trouble Adjusting the Thermostat

Speaking of the thermostat, glitches within the control center of your air conditioner could also pose a problem. Failure to turn on an AC unit that’s blowing warm air are both signs of a thermostat issue.

First, make sure your thermostat is calibrated correctly. Some people think that new, high-tech thermostats and SMART technology have replaced the need for calibration, but this simply isn’t true.

Even digital thermostats need to be properly calibrated to work efficiently. Calibration is what tells your home’s AC unit to turn on when the house hits a certain temperature.

If your thermostat is calibrated correctly but the AC still isn’t working, check that it’s set to the lowest possible temperature. This should kick start the unit. If not, it may be time to call in the experts.

HVAC repair technicians know how to recalibrate both older and newer thermostats. The digital varieties are sometimes more confusing than the older models. Have your owner’s manual handy to help the technician troubleshoot the problem.

Dirty, Leaking, or Clogged Air Ducts

Your central air conditioner sends refreshing, cool air through ducts to reach every room of your house. These ducts pull warm air from the house and carry it to your AC unit for treatment and cooling. If those ducts are dirty, clogged, or have a leak, air can’t travel freely.

Some homeowners don’t realize that tears and other obstructions can enter the AC ductwork. While most central air systems are sealed, rodents can make holes in the ductwork. Shoddy installation is another common culprit.

Holes or tears in the ductwork allow warm air to escape and release into your house. That’s why the first sign that there’s an issue with your AC ducts is uneven cooling.

Is one or more room in your house warmer than the others? This is a telltale sign of improper airflow.

Another sign that you may have damage to the air ducts is an increased electric bill. If your unit is working overtime to cool air that’s escaping through holes in the system, you’ll notice a spike in your electric bill.

Leaky air ducts can cause the same types of issues. You’ll need to inspect the air ducts to determine the level of damage.

When in doubt, call in the professionals to do a thorough inspection for you.

Drainage Issues

Leaks aren’t something most homeowners associated with their central air system, but leaks and drainage issues are common problems.

Air conditioners are designed to remove both heat and moisture from the air, but how? The unit uses a drain line to remove moisture. The moisture then drips into a pan and is then funneled into a drain.

A few problems can occur here. If the pan becomes full, it can overflow, and water will back up into your system. In some cases, the drain line shifts out of place, sending moisture to the surrounding area instead of into the pan.

The drain line can also become clogged, preventing proper drainage. Any of these issues can cause water leaks, damaging your home and belongings.

It’s important to check your unit’s drain lines regularly, especially if your home is unusually warm or you notice signs of a leak including stains on the ceiling or running water.

A Noisy System

Most central air systems run relatively quiet. You may hear a “swoosh” as the unit turns on and cool air floods from the vents and into your home. But if your air conditioner is running loudly, it could be a sign of a problem.

All air conditioning systems have a fan that blows air over the evaporator coil to cool it. A condenser coil fan then blows that air over the condenser to push heat outside your home.

Like with any mechanism, these fans can wear out, break, or become damaged. And when they do, you’ll know!

Fan motors are generally quiet, but when dirt and debris buildup, they can become quite noisy. Other issues include deteriorating fan motors or worn belts.

Once you troubleshoot and identify the issue with your AC’s fan, you may need an HVAC repair company to rectify the problem and prevent further damage.

Frozen Evaporator Coil

When things start heating up in your house, it may be the result of a frozen evaporator coil.

The evaporator coil contains refrigerant, which absorbs the heat being pulled from your home. If the coil doesn’t receive enough air or refrigerant levels are low, a layer of ice can develop. In some cases, the coil freezes completely.

The result is less cool air coming from the ducts or, in some cases, no air at all.

Check the Refrigerant Levels

Low refrigerant levels can also cause a problem for the evaporator coil and you. Refrigerant is more important to the function of your AC unit than most people realize. It’s the lifeline of your system like motor oil is for your vehicle.

First, check the refrigerant levels. If they’re low, it’s likely due to one of two reasons.

You either have a leak or the system was undercharged during installation. Unfortunately, unlike your car, you can’t just top off the refrigerant and call it a day.

You’ll need a professional HVAC technician to assess the issue and determine if it’s repairable.

Airflow Issues

If you discover that the refrigerant levels are fine, an airflow issue might be the reason for your frozen coil. The most common cause of insufficient airflow is a dirty filter.

It’s recommended you change your air conditioner filter every 90 days, depending on use. Homes with pets may need to change the filters more often, whereas vacation homes and rentals can extend the timeframe to every 6-12 months.

Once you change the filter, let the unit defrost. Next, check the evaporator coil for dirt and debris. If you notice a lot of buildup, clean it!

If you’ve tried all these AC troubleshooting tricks and the evaporator coil is still freezing up or you can’t identify the problem, call a professional AC repair company.

Take It Outside

One place most homeowners fail to check when performing AC troubleshooting is the outside unit itself.

Go outside and examine the unit. Is there any dirt or debris covering the surface?

If so, your air conditioner is probably working overtime to cool your house. Dirt and debris can also cause clogs and other complications.

Use a hose and gently rinse and remove any visible dirt. If you don’t normally clean your outdoor unit, you may notice a thicker than normal layer of dirt.

Don’t soak your AC in water! This could cause a whole list of other problems.

Put down the hose and call in the professionals to perform a deep cleaning. When your AC unit isn’t in use, invest in a cover to protect it from the outside elements. This can prevent unwanted dirt and debris from collecting on the unit and causing problems when you finally power it on.

Central AC Not Working? We Can Help

This article covers some of the most common AC problems and how to troubleshoot them. Some repairs are easy, which means you can perform them yourself and return to cool, comfortable living.

Other AC issues need professional intervention. When in doubt, don’t try to repair serious issues yourself.

You can also prevent the need for AC troubleshooting by performing routine maintenance.

Central AC not working? Don’t panic!

Just call the professionals at Service Champions and we’ll get your system back up and running in no time. We serve East Bay, South Bay and the Sacramento areas and have locations in Pleasanton, Livermore, Rocklin, San Jose, and Concord.

Related Reading