Causes and Solutions

There are many reasons that can cause your HVAC system to stop circulating cold air. Some are simple and can be taken care of easily, but others require the help of a professional. Here are some common issues to look out for:

1. Clogged Air Filter: A dirty or clogged air filter will restrict the airflow and put extra strain on your system. A very dirty or misplaced air filter could restrict airflow so much that the fan continues to run but no cool air comes out of the vents.
2. Dirty Unit and/or Coils: Coils can become dirty from dust in the air, tree sap, sticks, leaves and other debris, which can make the unit not work properly.
3. Faulty Thermostat: Your thermostat settings may be wrong, or the batteries may be dead or installed incorrectly.
4. Low Refrigerant Levels: Your AC will not blow cold air if you have a refrigerant leak.
5. Damaged Air Ducts: If the air is cool in some rooms but not in others, there could be an issue with clogged or damaged ductwork where your cool air is going into your attic instead of your living space.
6. Electrical Issues: A tripped breaker or blown fuse could be the cause of it not working.
7. Blocked Vents: Be sure nothing is blocking your vents. They must remain wide open, or the air conditioner won’t work properly.
8. Old Unit: You may need an upgrade. A new system is a major purchase, but the cost can be offset by the cost savings of increased efficiency.

Steps You Can Take

If you experience any of the above issues, here are some steps you can take on your own:

1. Change Air Filter: Air filters trap dirt and dust and other debris and should be changed every three months or sooner to ensure airflow isn’t restricted.
2. Clean Evaporator and Condenser Coils: Coils should be cleaned well at least once a year to ensure they’re clean and don’t grow mold.
3. Check Thermostat: Switch your setting to AUTO if your system is set to ON (fan mode). This should ensure your unit is only blowing cooled air into your home. A programmable thermostat might need to be reset to factory settings and then reprogrammed with your desired settings.
4. Check for Leaks: When there is a refrigerant leak, you may hear a hissing noise. Look for ice, which can build up if the evaporator coils are frozen. If you think you have a leak, turn off your AC and call a professional, refrigerant leaks can be toxic and make you sick.
5. Check Air Ducts: If you suspect there are gaps or cracks in your ductwork, an HVAC professional can properly seal any air leaks.
6. Check Cable: Make sure the cord is plugged in correctly and that there is no damage. There could be an issue with the electrical panel where it may need to be reset.
7. Replace Unit: If your unit is still acting up after trying everything, it may be time to replace your HVAC system. Typically, you’ll need $5,000–$15,000 upfront and out-of-pocket for your AC (not including ductwork repair or a new heating system), but there are other options. 

Preventative Measures to Maintain Your HVAC System

Your HVAC system needs regular maintenance to keep it running efficiently. It is recommended to have a maintenance tune-up twice a year (spring and fall) where the technician will make any repairs necessary before the weather gets hot or cold. Here are some maintenance practices you can do on your own:

• Schedule Regular Maintenance: Regular checks with a qualified HVAC technician will ensure your system is functioning properly and will identify any potential issues before they become major problems.
• Clean Outdoor Unit: Regularly clean and maintain your outdoor unit from debris. Once a month is recommended.
• Replace Air Filters: Change the air filters regularly to ensure adequate airflow and prevent dust and debris from accumulating on the evaporator coils. Every three months is recommended.
• Proper Insulation and Ductwork: Fixing ductwork leaks can help to improve performance and efficiency.

When to Call an Expert

If your air conditioner still isn’t blowing cold air but running after troubleshooting, it may be best to hire an experienced HVAC technician. Here are some signs where you should call a professional:

• Suspected Refrigerant Leak: Often accompanied by ice build-up, low refrigerant may indicate a leak in the system, which can be toxic and make you sick.
• Complex Electrical Problems: An occasional breaker trip is normal, but repeated incidents indicate bigger electrical issues and require a qualified professional.
• Unusual Noises: If your unit is making strange sounds or isn’t running at all, you may need a replacement.
• Damaged Ductwork: An HVAC technician can thoroughly examine your ductwork to identify and repair blockages, leaks or other damage.
• Thermostat Malfunction: An expert can see whether your thermostat’s wiring needs repair, or if the entire unit needs replacing.

There are many reasons that can cause your AC not to blow cold air, and the fix can be simple or quite complex. If you aren't sure what the problem is, have your local Lennox pro come and assess the situation and help get cold air moving again in your home.