How to Know If Your AC Isn’t Working

When summer hits and temperatures soar, your air conditioning becomes one of the most important systems in your home. But what happens when your AC unit doesn’t seem to be keeping up? Sometimes it’s obvious your air conditioner isn’t working—but other times, the signs are subtle until it’s too late.

Knowing the early warning signs can save you from expensive repairs and unbearable indoor heat.


Warm Air Coming from the Vents

If your AC is blowing warm or room-temperature air, that’s a red flag. It could be something as simple as a thermostat set to "heat" instead of "cool," or a more serious issue like:

  • A faulty compressor
  • Low refrigerant levels
  • Restricted airflow

Check your thermostat first. If that’s not the issue, it’s time to call a technician.


Weak or No Airflow

Poor airflow means your AC system isn’t distributing air properly. This could be due to:

  • A clogged air filter
  • A failing motor
  • Leaky or blocked ducts
  • Dirty evaporator coils

If some rooms are cool while others aren’t, your ductwork might be the problem.


Strange Noises

Air conditioners aren’t silent, but they shouldn’t be making banging, grinding, screeching, or rattling sounds. These noises often indicate:

  • Loose parts
  • Worn-out belts
  • Debris stuck inside the unit
  • Fan motor issues

Turn off the unit and schedule a repair before more damage occurs.


Unpleasant Odors

If your AC gives off a musty, burnt, or sour smell, that’s a warning sign. Possible causes include:

  • Mold or mildew in the ducts or unit
  • Burned-out wire insulation
  • Clogged drain lines

A foul smell could impact your indoor air quality and your health.


Frequent Cycling

It’s normal for an AC to cycle on and off to maintain your set temperature. But if it’s happening every few minutes, something’s wrong. Common causes include:

  • Incorrect thermostat settings
  • Refrigerant issues
  • Dirty filters
  • An oversized AC unit

Frequent cycling puts extra strain on your system and increases energy bills.


High Humidity Indoors

One of the functions of an AC unit is to remove humidity from the air. If your indoor environment feels sticky and humid even with the AC on, you may have:

  • A malfunctioning AC sensor
  • Refrigerant problems
  • An oversized or aging unit

Humidity issues can also lead to mold growth and discomfort.


Rising Energy Bills

If your energy bills suddenly spike but your usage hasn’t changed, your AC may be running inefficiently. Reasons include:

  • Clogged filters
  • Refrigerant leaks
  • Old, outdated equipment
  • Poor insulation or leaky ducts

Energy efficiency problems usually worsen with time, so don’t ignore them.


Water Leaks or Ice Buildup

You should never see water pooling around your AC unit. And ice on the coils is just as bad. These symptoms could point to:

  • Blocked or cracked drain tubes
  • Dirty coils
  • Low refrigerant
  • Frozen evaporator coil

Water and ice can damage your unit and cause mold or mildew near the system.


Thermostat Issues

Sometimes the problem isn’t with the AC itself, but the thermostat. If the system isn’t responding to changes or the display is blank or flickering, it could be:

  • A faulty thermostat
  • Dead batteries
  • Electrical wiring issues

A malfunctioning thermostat can prevent your system from cooling your home at all.


AC Unit Won’t Turn On

This is the most obvious sign something’s wrong. If your AC doesn’t power on:

  • Check the circuit breaker
  • Ensure the thermostat is set correctly
  • Look for signs of blown fuses or electrical failure

If none of those solve the problem, contact a licensed HVAC technician immediately.