In the dog days of summer, it’s frustrating when you must ask, “why is my AC not cooling?” In this blog we’ll review some common causes, DIY fixes and when to call a pro. 

There are several reasons a central air system stops cooling effectively, so we’ll begin with steps you can take before you call for AC repair from a professional HVAC contractor. 

AC DIY TROUBLESHOOTING TIPS

  1. Check the thermostat
  2. Clear debris from the AC compressor outside
  3. Check the air filter
  4. Verify vents and returns inside are unblocked and open
  5. See if the circuit breaker tripped

IF AC BLOWS WARM AIR OR WON’T TURN ON; CHECK THE THERMOSTAT

In some cases, an air conditioner turns on, but only blows warm or lukewarm air. Why is the AC not cooling? It could be because the thermostat is incorrectly installed or on the wrong setting. 

AC Troubleshooting Fix

Verify the thermostat is set on “COOL.” Frequently, the lever or button is accidentally bumped by someone or even a vigorous duster! Plus, it’s easy, during spring and fall when our weather yo-yos a bit, to reset the thermostat after a temperature swing. 

Also, check the fan setting. If the fan is set to “ON” instead of “AUTO” it runs 24 hours a day. In other words, the fan runs even when the air conditioner isn’t cooling. 

In some cases, the thermostat is installed in a poor location, which impacts its ability to draw a true, ambient average temperature. Thermostats should be in interior rooms, away from windows, or in a hallway. Make sure there’s nothing nearby that could give off additional heat or even cooling, to confuse its temperature sensors. 

Conclusion: Set thermostat on “COOL,” and the fan to “AUTO.” 

IF AC STRUGGLES, HAS WEAK AIR OUTPUT; CHECK THE AC COMPRESSOR OUTSIDE

The AC compressor unit outside pumps the hot air out of your house when the air conditioner cools your house. If you use a heat pump, the compressor runs all year because a heat pump performs like an air conditioner in the summer but reverses the process in the winter. 

In that case, the heat pump draws warm air from outdoors through the compressor and into the air handler where it’s distributed through the ductwork? How is that possible in colder states? 

Believe it or not, heat pump technology continues to advance and keep many northern homes comfortable in every season. For example, during extreme temperatures, heat pumps draw on an auxiliary heat source, called electric heat strips. Air passes over the strips, just like a heat exchanger in a furnace, and absorbs the heat. 

Regardless, heat pumps use the AC compressor unit all year. Therefore, it needs optimal airflow.

AC Troubleshooting Fix

Walk around the outdoor AC compressor unit. Clear away dirt, debris, fallen leaves and anything that’s collected around it. Too much vegetation or dirt “chokes” the AC compressor. It needs to “breathe” so make sure it’s clean. 

  • Locate the power switch; it’s usually inside a metal box near the AC compressor unit. Turn it off.
  • Using a hose, gently spray away pollen, dirt and anything cluttering up the AC compressor fins and the base. Do not use a power washer. That is way too much force. 
  • Remove flowers, plants, or shrubs so that the AC compressor has a buffer zone of two to three feet.
  • Make a habit of walking around the AC unit after storms to remove fallen leaves and twigs. It’s easy for twigs, for example, to end up inside the AC unit and cause problems with the fan blades. 
  • Trim any nearby branches if they’re leafy, thick or look like they’re dying. All it takes is a good storm and a heavy branch could really damage your AC compressor. 
  • When finished, let it dry as much as possible before switching it on again. 

dirty AC compressor | Why is My AC Not Cooling | Air Conditioner Troubleshooting Tips | A-1 Mechanical | Grand Rapids Lansing MI

Conclusion: Clear away yard clutter and clean the outdoor unit.

Image credit: Invertedaircon.com.au

POOR AIRFLOW, AC SHUTS OFF EARLY OR AIR CONDITIONER FAILS TO FULLY COOL HOUSE; CHECK THE AIR FILTER

Similar to the AC compressor, your indoor components depend on good airflow. A clogged filter prevents air from easily passing through. The HVAC system strains to force air through the dirty filter. This puts excess wear and tear on your equipment, circulates contaminants and creates a lot of problems, including frozen evaporator coils. 

AC Troubleshooting Fix

We recommend you check the filter in your HVAC system every month. Use the arrival of a gas or electric bill as a reminder. Most homes find a filter change every two to three months is sufficient. If your household includes smokers, pets or members sensitive to high pollen and other asthma and allergy triggers, change it more often.

why is my ac not cooling | Air filter dirty clean | A-1 Mechanical Heating and Cooling | Lansing Grand Rapids, MI

Conclusion: Check your air filter and change it as needed.

Left: Dirty filter, Right, New filter. Image credit: Pinterest

AC NOT COOLING, HOT OR COLD SPOTS IN THE HOUSE; CHECK AIR VENTS

It’s common for furniture, drapes or temporary items like toys, to block air vents in the house. Again, obstructions to airflow cause your HVAC system to work harder, increasing the likelihood of an AC repair. 

It’s common to have blower motor issues, frozen evaporator coils or water leaking from your air conditioner due to poor airflow. Return vents are usually larger squares or rectangles and draw air into the ducts. 

They are sometimes high on the wall, but sometimes below knee-level. Supply vents are the smaller rectangle vents on the floor or up high on the ceiling.

AC Troubleshooting Fix

Walk around the house and check all the return and supply vents. Move anything blocking airflow and make sure they’re open. Sometimes homeowners think closing vents in rarely used rooms saves money. It actually disturbs the air pressure in the home and creates more problems. 

Conclusion: Keep air vents unblocked and open. 

AC NOT COOLING, WON’T COME ON OR SHUTS DOWN QUICKLY; CHECK CIRCUIT BREAKER BOX

Did you know the most power surges come from within your own home? Sure, lightning and external power grid issues occasionally blast power into your home, but the majority of the time, it’s your own appliances. Large appliances, like air conditioners, push a power surge through the system when they start up. If your air conditioner stops abruptly, it could be an electrical problem. 

AC Troubleshooting Fix

Find the main electrical panel for your house and look for circuit breakers in the OFF position. If you’re lucky enough to have clearly-labeled circuit breakers, look for “AC” or “Air Conditioner.” If it’s tripped, push the breaker into the “ON” position and see what happens. 

Conclusion: It’s possible a one-time event tripped the circuit breaker. If, however, the breaker immediately trips again when you try to run the AC, turn off the air conditioner and call a professional. It’s likely you have an electrical issue. 

COMMON AC NOT COOLING ISSUES FOR PROS

If the DIY AC troubleshooting tips haven’t resolved your issues, it’s best if you call professionals for help. Common air conditioner problems causing your AC to not cool your home include: 

  • Refrigerant problems. It could be a leak or low charge. Regardless, refrigerant is a toxic chemical and you don’t want to mess with it. Call an HVAC technician. 
  • Fan motor issues. If the fan motor is broken or suffering from electrical issues, it can push cool air through your house. Call an HVAC technician. 
  • Bad capacitor. If the capacitor is bad, your AC isn’t getting the power it needs. You need a replacement from an HVAC technician. 
  • Worn out AC compressor. The compressor is a major component and often under a separate warranty. Call an HVAC technician to see if it can be saved. If not, you may need to consider an air conditioner replacement.

    Weigh the cost of repair against the cost of new air conditioner installation. Consider with a new AC you’ll get a new warranty and if it’s more energy-efficient, lower AC bills immediately. 

AC STILL NOT COOLING? CALL A-1 MECHANICAL 

If these central air conditioning troubleshooting tips haven’t solved the problem, call our team in Lansing or Grand Rapids for help. We’re eager to help when you find your AC not cooling effectively. We offer a range of heating and cooling services to our communities including air conditioner installation, AC service and repair

For a free estimate on new HVAC equipment or to book AC repair or service, call A-1 Mechanical at 517-348-0302.