Post: How to Diagnose Central Air Conditioning Problems

Diagnosing your Central AC Problems

At Pileiro Heating and Cooling, our goal is to be your trusted HVAC contractor for every need, whether you’ve had an emergency breakdown in the middle of the night or you need recommendations on the most energy-efficient equipment for your home. 

We’re also proud to use our expertise to help our customers troubleshoot some issues they may encounter over the lifespan of their central air conditioning system. Read on to learn more about how to diagnose air conditioning problems, so you can become a more informed property owner.

Common Issues That May Arise

There are a number of issues that commonly arise with central air conditioning systems. We’d listed them in the easy-to-read table below. If you’re after a full breakdown though, you can continue to read this whole article.

ProblemPossible CauseSolution
AC Won’t Turn OnThermostatClogged filterTripped breakerCheck your thermostat settings.Change your air filter.Turn your circuit breaker off, then back on.
AC Isn’t Cooling Dirty condenserRefrigerant leakImproperly sized unitClean the condenser.Turn off the AC and call a professional.Consult with a technician.
Poor Air CirculationLeaky or disconnected ductworkBroken motor or compressorClosed dampersContact a professional for ductwork repair.Call your HVAC technician to inspect your AC.Check the dampers and make sure they are all open.
AC Isn’t Dehumidifying (Oversized Unit)A unit that is too large for your home will cool the air in rapid cycles, which doesn’t allow time to remove moisture.Purchase a properly sized unit.Ask an HVAC pro about a whole-house dehumidifier.
AC Isn’t Dehumidifying (Correctly Sized Unit)Low refrigerantOlder AC can’t keep upDirt in the systemCall an expert to check your refrigerant charge.Consider whether it’s time to replace your system.Have an AC tune-up performed.

Your AC Unit Won’t Turn On

If your air conditioner fails to come on, it can be frustrating, especially during the hottest part of the summer. Air conditioners are complex machines with many moving parts, so it stands to reason several things can go wrong — especially with an older or poorly maintained system. What can you do if your AC won’t turn on?

Possible Causes

  1. Thermostat
  2. Clogged air filter
  3. Tripped circuit breaker


  1. Check that your thermostat is on, has power, is on the cool setting and has the temperature set several degrees below the current room temperature.
  2. If your air filter gets clogged, it can prevent adequate airflow in your home. An air filter can look clean, even if it’s not, so it’s a good rule of thumb to replace this filter every three months.
  3. A sudden power surge can trip your circuit breaker and cut off the power to your AC unit. Locate the correct circuit breaker, turn it all the way off, wait a few seconds, then switch it back on.

Your AC Unit Isn’t Cooling Your House When Turned On

You rely on your AC to keep you comfortable when it’s hot outside. But what if your air conditioner is running, but not providing cooled air? 

Possible Causes

  1. Dirty condenser
  2. Refrigerant leak
  3. Improperly sized AC for your home


  1. A dirty or clogged air condenser makes it much more difficult for your air conditioner to function effectively. First, sweep around your outdoor unit and make sure to clear away all dirt and debris. Next, carefully clean the condenser using soapy water.
  2. Refrigerant enables your air conditioner to absorb the heat from the air. If ice has formed on the outside of your unit, you might have a refrigerant leak. If you suspect this is the case, turn off your unit and contact a professional immediately.
  3. If your AC is too large or too small, it will struggle to reach your desired temperature, and will experience excessive wear and tear that shortens its lifespan.
Stressed couple trying to refresh from summer heatwave

Your AC Unit Has Poor Air Circulation

Is the airflow in your home uneven from one room to the next? Perhaps poor circulation is the problem. There are a few straightforward reasons this can happen, including the following.

Possible Causes

  1. Leaky or disconnected duct work
  2. Broken motor or compressor
  3. Closed dampers


  1. The duct work’s job is to help your AC distribute cooled air to the vents in your home. Leaks, gaps or cracks in your duct work allow the air to escape before it reaches its destination. When you have this problem, you should contact a professional for diagnosis and repair.
  2. Sometimes, components of your air conditioner can fail without warning. It can be challenging to diagnose this kind of problem if you aren’t a trained HVAC technician, which is why you should always call someone with the right tools and equipment to do the job.
  3. Dampers are valves in your duct system. If they mistakenly get closed, they will restrict airflow to a room or vent. Make sure your dampers are open, and see if that fixes the problem.
worker in the attic connects metal air ducts

Your AC Isn’t Dehumidifying Air (Over-sized System)

If your central AC is running, but you still feel sticky and sweaty, your AC unit may be cooling your home too quickly because it’s too large. You may think bigger is always better, but when it comes to your home comfort, that isn’t true.


It takes time to dehumidify the air and remove enough moisture for you to be comfortable. However, an oversized unit will have much shorter cycles than a unit that is the correct size for your home, allowing water to be carried back into the air. Aside from high humidity issues, an oversized unit also costs you more in energy and maintenance expenses, and will probably have a shorter lifespan than a properly sized system.


The primary solution for an oversized system is to work with a qualified HVAC contractor to purchase a new, smaller-capacity unit that provides more efficient cooling and dehumidifying. However, if you haven’t budgeted for a replacement AC, ask your AC technician about the benefits of a whole-house dehumidifier.

Your AC Isn’t Dehumidifying Air (Correctly Sized System)

What happens if you own a properly sized AC and you’re still experiencing excess humidity in the air? There are a few things you can check on.

Possible Causes

  1. Low refrigerant
  2. Your older AC can’t keep up
  3. Dirt and debris in the system


  1. An AC with a low refrigerant charge won’t be able to dehumidify the air as well as a fully charged unit. If you need more refrigerant, call a trained pro.
  2. As your air conditioner ages, it may not run as efficiently as it used to. That tendency increases if you haven’t kept up with your seasonal AC maintenance. In addition to inconsistent temperatures and inadequate cooling, you’ll start to notice poor HVAC humidity control with an older AC system.
  3. One of the best ways to prevent damage to your system is to ensure its components are all clean. If the internal workings are covered in gunk, they won’t work efficiently, and a lack of dehumidification is one possible consequence. We can clean your unit during an AC tune-up.
Man working on air conditioning unit

Areas to Troubleshoot

Rather than calling in the experts right away, there are some key areas that you can troubleshoot yourself. You might to discover an easy-to-fix problem, or at least you will be able to zero-in on what’s causing your AC issues. Below, we discuss the various parts of the air conditioning system that you can inspect on your own.

Air Filter

The air filter is one of the most common culprits associated with AC troubleshooting. If you’re experiencing issues such as low airflow or an air conditioner that doesn’t run efficiently, your air filter should be at the top of your DIY home maintenance checklist. Check your AC’s instruction manual for the manufacturer’s recommendations on how often to change your filter. Some may suggest replacing filters as often as once a month, while others might say to do so every three months. Either way, put a reminder on your calendar to ensure a properly functioning air conditioner.

Thermostat Settings

Before calling a cooling expert to inspect an apparently faulty air conditioner, check your thermostat first. It’s easy to assume the worst-case scenario when it comes to your AC, but a straightforward thermostat adjustment could be all you need to get your home cool and comfortable again. If your AC isn’t running properly, make sure you have your thermostat set to “auto” and “cool.” If the thermostat’s display isn’t lit, double-check the batteries or the circuit breaker to ensure it’s getting power. Call a HVAC tech if you’ve done these basic steps and you still aren’t sure you’ve resolved the problem.

AC Circuit Breakers

A circuit breaker is a safety feature that can protect your home’s appliances by turning off the electricity when it detects a sudden power surge. If your AC won’t come on, it might be due to a tripped circuit breaker. Here’s what you can try.

  • First, turn your air conditioning system off at the thermostat.
  • Find the correct circuit breaker switch for your AC, and turn it to the on position.
  • Wait at least 30 minutes with the air conditioner off. This waiting period gives your AC’s internal circuit breaker time to reset without the thermostat signaling it to resume cooling. 
  • After half an hour, set your air conditioner back to cool.

Ideally, everything will work normally after these steps. However, if the breaker immediately trips again, or the AC won’t come back on, contact the pros at Pileiro for diagnosis and repair.

Outdoor Unit

Outdoor AC units from today’s top manufacturers undergo rigorous testing to ensure they can withstand extreme weather conditions. However, you can still take some proactive steps to protect your outdoor unit against damage. 

  • Keep the area around your AC free from debris throughout the year. Periodically check it to sweep away dirt, dead leaves, twigs, grass clippings, etc. 
  • Remove any vegetation growing on or near your unit. Do not overplant shrubbery or other landscaping elements that could block the airflow. A best practice is to maintain at least an 18-inch clearance around the outdoor unit. 
  • Regularly inspect and maintain your gutters to ensure they are not leaking onto your AC. 
  • Trim any trees that are growing near the air conditioner and remove dead branches to prevent a falling limb from damaging the unit in inclement weather.

Air Vents

Cleaning your air vents is another DIY task you should have on your to-do list if you’re concerned about the air quality in your home. Here’s how. 

  • First, turn off your HVAC system.
  • Then, remove the air duct covers and use a brush to clean them thoroughly. If they’re still dusty after brushing, try washing them with water and a bit of dish soap. 
  • Vacuum the ducts with a hose. If you want a more thorough cleaning to prevent the buildup of mold or other allergens, consider hiring a professional to do the job.
  • If you have any vents in your ceiling, don’t forget to clean those as well. If you can’t reach them with the hose attachment on your vacuum, use a broom to sweep away the dust. Remember that if it’s been a while since your last cleaning, it’s smart to wear a dust mask to protect yourself from falling debris.
Mature man examining an outflow air vent grid and duct to see if it needs cleaning. One guy looking into a home air duct to see how clean and healthy it is.

Need someone to solve your AC problems? Choose Pileiro!

If you’re searching for reliable AC service, repair and installation in the South Jersey area, the team at Pileiro Heating and Cooling wants to be the first and only call you make. We are well-versed in all the major makes and models of air conditioners, including Trane and Mitsubishi, and we are proud to maintain a membership with the Air Conditioning Contractors of America — the nation’s leading trade organization for the heating and cooling industry. If you live in Cape May or Atlantic counties and need expert, 24/7/365 help with your AC, we want to hear from you.

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