Air Conditioner Troubleshooting: Why Your AC Is Not Cooling

If your AC is not blowing cold air or is simply not working or turning on, we can help. Save time and money by learning AC fixes you can try yourself. This air conditioner troubleshooting guide details common AC problems and solutions needed to get your home back to its ideal comfort.

There are many possible reasons your AC is not cooling the house. In an air conditioning system, many parts work together to help your air conditioner function properly, and if something goes wrong with one, it could impact the entire system. If your AC is not cooling the house, some common AC problems homeowners face might be that the filters are clogged, the refrigerant is leaking or low, or the coils are frozen or dirty — and that’s just the beginning.

What you can do

If you are experiencing an issue with your Trane system, the below troubleshooting guide can help answer your common AC questions with possible solutions. If none of these AC troubleshooting tips work, contact an HVAC technician to get AC repair or replacement help from an expert.

If your AC is not blowing cold air or running correctly, it could mean you have one, or more, of the following issues:

• The outdoor cooling coil may be clogged or blocked
• The indoor air handler coil could be blocked
• The filters may be clogged or dirty
• The thermostat controls may be set incorrectly
• The refrigerant might be leaking or low

What you can do

Here are some tips to help you troubleshoot issues why your AC is not blowing cold air and not running:

• The outdoor cooling coil may be clogged or blocked

  Debris can easily stick to the inlet side of the cooling coil in your unit. Be sure to clear away any tall grass, sticks, or leaves that may be surrounding your outdoor unit.

• The indoor air handler coil could be blocked or not working

  Ordinary house dust and debris like soot or pollen can block indoor air handler coils. For your indoor air handler, try to wipe away any buildup of dust on the coil and change the air filter often.

  The air handler might also not be working because of a blown fuse or open circuit breaker. Reset the circuit breaker or replace the burned-out fuse. You should also check return grills for blockages that could keep air from circulating freely in the system.

• The filters may be clogged or dirty

  Set your AC to “OFF” and turn off the breakers that supply it with power. Clean or replace the filters. Consult your local Trane Comfort Specialist™ if you are unsure where the filters are located.

• The thermostat controls may be set incorrectly

  Try turning the thermostat off and then on again. Reset to the desired temperature and see if that helps.

• The refrigerant might be leaking or low

  If your AC is not blowing cold air, the refrigerant may be the problem. The unit could be running low and need additional refrigerant added. The most likely cause of this is a leak. A leak not only keeps the AC unit from cooling properly but also can cause other issues within the home, such as rising humidity levels. If you suspect a refrigerant leak, contact an HVAC professional to repair the unit immediately.

If your AC is not turning on, it could mean you have one, or more, of the following issues:

• The thermostat is not turned on or has dead batteries
• The circuit breaker is tripped
• The condenser unit is unplugged
• The air filter is clogged
• The AC drain line is clogged
• The AC has a motor failure

What you can do

Here are some tips to help you troubleshoot why your AC is not turning on: 

• The thermostat is not turned on or has dead batteries

  Check your thermostat to see if it is off or showing a blank display. If it is, try to switch it on. If the thermostat does not turn on, it could also have dead batteries. Replace the batteries in the thermostat to see if that fixes the problem.

• The circuit breaker is tripped

  A common problem is the circuit breaker switching on and off, especially when you’re using too many appliances at once or there power surges after a storm. Locate your electrical panel and check the AC switch. If it is in the “OFF” position, switch it “ON.” If the circuit continues to trip the circuit might be overloading. Call an electrician immediately in this instance to troubleshoot further and prevent electrical issues.

• The condenser unit is unplugged

  If you cannot see a cord coming out of your AC, your AC may not be plugged in. Check to see if there is a small cord coming from your AC that is connected to a panel on the side of your home. Note that these wires can become unplugged or even chewed through by animals.

• The air filter is clogged or dirty

  Set your AC to “OFF’ and turn off the breakers that supply it with power. Clean or replace the filters. Consult your local Trane Comfort Specialist™ if you are unsure where the filters are located.

• The AC drain line is clogged

  Lack of maintenance will cause the AC drain line to clog with debris and other gunk. You can keep your condensate drain line clean by pouring a cup of boiling water down your drain pipe every month or so. Before you do this, be sure to turn off the air conditioner and power supply to the unit. It’s always a good idea to consult your local HVAC technician for help unclogging the AC drain line.

• The AC has a motor failure

  A capacitor charges your AC’s motor and if your AC system’s life span is up, a faulty capacitor could be the culprit for its failure to turn on. In this case, a professional technician can help you diagnose if this is the problem.

Remember that an expert HVAC technician is trained to help you if your AC is not turning on. Keep in mind that servicing an AC system can be dangerous and a professional technician is trained in servicing an air conditioning system.

If your air conditioner is running or won’t turn off, but not lowering the temperature inside your home, there are a few things that could be the problem:

• The thermostat is set incorrectly
• The air filter is dirty
• The condenser unit is blocked
• The AC unit is undersized
• The refrigerant might be leaking

What you can do

Here are some tips to help you troubleshoot why your air conditioner is running, but not lowering the temperature inside your home:

• The thermostat is set incorrectly

  Check your thermostat setting and make sure it’s set to cool. If it is set to cool, check the thermostat setting to make sure it’s at your desired temperature. If it’s not set to cool, switch to cooling operation.

• The air filter is dirty

  Set your AC to “OFF’ and turn off the breakers that supply it with power. Clean or replace the filters. Consult your local Trane Comfort Specialist™ if you are unsure where the filters are located.

• The condenser unit is blocked

  One issue could be a blocked or clogged condenser coil. When operating correctly, the condenser fan draws air into the outdoor unit through the condenser coil to pull heat energy out of your home.

  If you suspect the condenser unit is blocked, contact a professional technician to have them professionally clean the coil. The AC fan may also be to blame.

• The AC is undersized

  Air conditioners are sized according to the amount of cooling they provide in BTUs. Sometimes, ACs are not the ‘right size’ for your home, depending on a number of factors, including square footage, quality of construction and insulation, local climate, and more.

  The best way to address sizing issues is to connect with a qualified HVAC professional who can assess your home and its optimum cooling capacity. In some instance, you may be able to add ductless units to the home to assist in the cooling, or you may need to replace the air conditioner system with one that’s the right size.

• The refrigerant may be leaking

  Refrigerant is a chemical that is instrumental in the cooling process as it flows through the AC system’s indoor and outdoor coil, changing from liquid to gas form, drawing heat and humidity and releasing outdoors. A refrigerant leak could be the culprit of the house not cooling properly. This issue is another job for a professional HVAC technician.

The drain pan below your interior AC unit collects condensation. An electric pump is supposed to move this condensation to a nearby drainage pipe. The pump might have come unplugged or there may be kinks or blocks in the drainage line. Contact your local Trane Comfort Specialist™ if you need help.

A number of factors could be causing a bad smell to come from your air conditioner. While some smells — like a musty scent the first time you turn your AC on for the season — are nothing to be worried about, other odors can be dangerous. Your air conditioner could be releasing a burning smell due to an electrical issue, or smell moldy because of bacteria growth inside. If you smell anything unpleasant coming from your air conditioner, turn off your system and contact an HVAC professional immediately for help.

Air conditioner troubleshooting can be a tedious task and, unfortunately, sometimes air conditioner malfunction isn’t preventable, despite all efforts. But, you can still take action to help mitigate problems and prevent them from occurring as frequently. Regular AC maintenance, done by both you and a professional, will help prevent AC issues. Plus, investing in a high-quality system with a good SEER rating will also lessen the chances of frequent issues occurring in your system.

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