There can be many causes of your air conditioning unit blowing warm air. We can’t cover all of them in this article, but we’ll address the most common ones.
1. Check your Thermostat. Is the display visible? if not, try changing the batteries, then check again. Are there loose wires or connections on the baseplate attached to the wall? Thermostat manufacturers include a wiring diagram if you get lost or are unsure of what goes where. Some thermostats have a time delay built in to them to prevent short cycling the compressor. Wait five minutes then check system again if you’ve recently raised or lowered the temperature
2. Check to see if your outdoor unit is running. Chances are, if this unit isn’t running you won’t be getting cool air. Your central heating and air conditioning unit is made up of different components. Residential a/c systems are usually called split systems. The outdoor unit houses your compressor and condenser fan motor. If the unit is dead, but you hear a humming sound coming from it. Check the breaker at main panel to ensure you have power going to the unit. Chances are most times, a capacitor has gone out on it. pull your service disconnect to kill power to condenser and inspect the condition of the capacitor (a silver cylindrical object in the control panel of condenser.) often times you can determine if its bad if it appears to be bulged out at the top. Other ways of testing involve a special meter designed to read capacitance, measured in mFd. When in doubt, change it out. Other causes of the outdoor unit not working are; a burned out condenser fan motor (intermittent, or non-functioning completely) a bad compressor, and a bad contractor.
3. A dirty condenser coil can cause the compressor to go off on thermal overload. This condition is caused by lack of routine maintenance. be sure to have your A/C system serviced at least every year or two. Part of this maintenance should include washing the condenser coils on your air conditioning systems outdoor unit.
4. Check Thermostat wire connections at outdoor unit. Dogs love to chew things. One of those things could be the low voltage control wires going to your outdoor unit. If you notice wires with bare copper showing or insulation peeling off them you may have suffered a short in the low voltage system. This can be a relatively inexpensive fix, but would require a professional’s assessment.
5. Look for ice build up on the line set running to the outside unit, or around the compressor. This can be a sign that your A/C system is running low on freon. The refrigerant you have in your system runs in a closed loop, and is a constant volume. Unless of course you have a leak in your system, or an excessively dirty air filter. This situation should be properly assessed by a local service professional. If its been a while since your last filter change, remove it from the system, and wait a couple hours before restarting the system. This is a very common condition found in many homes. Often systems 10 years of age or older suffer from small leaks in the evaporator coils on your air conditioning unit. This causes the icing condition, which can restrict airflow coming from the vents.