Air conditioning units are designed to cool down your home by chilling air from outside your home and then moving it through your ducts to various rooms in your house. However, there is a variety of problems and malfunctions that can cause your air conditioning system to fail to cool down the air it pulls in, resulting in warm air being moved throughout your home instead. There are many reasons that this can happen, each of which can be fixed in a different way.
The most common reason why your air conditioner will begin to blow warm air is because the refrigerant has leaked out of the system. This is almost always caused by wear and tear on the joints and connections within your unit, but can also be caused by improper installation on new units as well. There is no real way to determine if you have a refrigerant leak or not, but if your air conditioner is inexplicably blowing warm air with a properly functioning thermostat and no other visible signs of damage to the unit itself, you should call a HVAC professional to take a reading of your refrigerant levels and fix the leak to get your system working properly again.
Another common reason for an air conditioner to begin to blow warm air is if it has become frozen. This can occur when your unit is working at too high of a setting, causing the internal temperature to drop and the condensation within the unit to solidify on your condenser coils. In order to fix this, you should just turn the unit off for an hour or two so the ice can melt: in order to prevent it from happening again in the future, drop the temperature on your thermostat so that your unit is not working overtime again. If your unit continually freezes, you may want to contact a professional to inspect it.
Finally, a breaker that has been tripped can cause a central air conditioning unit to blow warm air by turning off the outside condenser, while still allowing the internal fan and circulation system to operate. This means that your air conditioner will simply be moving air around your home without cooling it down, much like a giant fan. Simply check the breaker box to see if any of the breakers have been tripped, and reset them if this is the case. If this happens constantly, you may want to contact an electrician like AAA Home Services to inspect the wiring within your home.