What to Do If Your Central Air Isn't Blowing Cold Air

A hot summer day is not the time you want to feel warm air coming out of your air conditioning ducts. The temperature is rising, both inside and out, and the do-it-yourselfer in you wants to troubleshoot before calling in an expert. An air conditioning system is complex, but there are checks and balances you can perform to avoid the dreaded warm air blowing on a hot day syndrome.

How an Air Conditioner Works

The unit sitting outside your house, the compressor, pulls in the warm air and then goes to work. Through mechanical magic, it changes that warm air into cool air and sends it into your home. The interior unit houses the fan, and it blows the cool air through your complex ducting system. The thermostat directs the temperature and the filters make sure only clean air is run over the interior coils.


Step 1

Check the thermostat. You don't want a "duh" moment when you discover that the cool switch has slid over to heat or fresh air mode. Be sure the temperature set to produce cold air; then knock it down about five degrees more to see if you can get cold air coming out. Verify that the auto switch is activated. You don't want the fan on at this point. If this step doesn't produce cool air, move on.

Step 2

Pull out the air conditioner's filter. It should be clean, devoid of pet hair, and allow air to move easily through it to the unit. If not, change it and wipe down the intake vents so only clean air passes through.

Step 3

Check your electrical panel to see if there is electricity going to the unit. Go outside to the unit and make sure it's plugged in and running, and that the fan is turning.

Step 4

Clear any debris from around the unit to avoid blockage of the vents. Check for puddles around the base of the unit that may indicate a leak.

Step 5

Check all the duct work in your house. None should be closed as that causes the air to divert itself and may cause the coils to freeze.

Step 6

Once the above steps have been taken and you've remedied any of the problems you've discovered, but the unit still isn't working properly, it's time to dive deeper into the mystery of the disappearing cold air.

Coil Problems

Your coils may have frozen. Symptoms of frozen coils are:

  • Buildup of ice on the interior of the inside unit.
  • The sound of constant drainage from the inside unit.

This can be caused by one of several scenarios:

  • Air flow has been obstructed. A dirty filter, blocked condenser, or a damaged blower motor are frequent culprits. A clean filter can prevent a frozen coil but won't remedy one.
  • Blocked air ducts.
  • Closed vents.
  • A fan that isn't working.

Do not attempt to clean the coils yourself. You may cause more damage, which can be expensive to repair. Instead, turn the thermostat to fan and call an air conditioner professional. The fan will melt the ice if you do have frozen coils, making the repair quicker and easier.

Refrigerant is low

Also known by its old name, freon, the refrigerant chemical is the facilitator that turns the warm air into cool air. Just as in your car, the refrigerant can run low through use or a leak. The types of refrigerant used in air conditioners is in transition, with older units using R-22. Known as an ozone depleting chemical because of its chlorine content, R-22 is being replaced with R-401a. Considered ozone friendly, R-401a contains no chlorine. </ahref="http:>Changing the refrigerant is complex and should be handled by a professional.

Your thermostat needs replacing

  • Turn off the power to the air conditioning system.
  • Open the thermostat cover and find the yellow (y) and red (r) wires. Disconnect them and twist them together.
  • Turn the power back on. If the blower starts up, your thermostat is faulty. If it doesn't, then the problem is not the thermostat.

Unless you are well-versed in electrical and wiring matters, replacing the thermostat should be handled professionally.

Faulty Duct Work

The return duct is the spot where air is sucked in within the house and passed over the coils, cooled and then sent out through the vents. If it's pulling in un-cooled air from the attic, the unit must work harder to cool this unprocessed air.

Climb into the attic and check the duct work for your system. Look for any collapsed section that may block airflow, holes or leaks and repair them as necessary. Do not clean the duct work yourself, especially if you live in Florida, and if the ducts are fiberglass. The process may stir up and loosen the fiberglass, a suspected carcinogen or cancer-causing agent.

You can prevent warm air from showing up when cool air is preferred by having a maintenance contract with an air conditioning specialist. These professionals perform yearly maintenance and checks of your system. If you do have a problem, your air conditioning person will most likely show up at your house before calling on someone who doesn't have a service contract. In the long run, it's less expensive than repairing a major problem. Change your filters yourself monthly and wipe the intake slats clear of dust and debris.