What’s worse than an air conditioner that doesn’t work at all? An air conditioner that doesn't work in 100 F weather. Seriously, I have been there.
Its pure science, if its too hot or too cold than this will be the time your system decides to break down.
Before calling an expert there are a few quick checks you can do to make sure it's not an easy fix and possibly save some money.
1. Thermostat Settings
Not blowing cold air? It could just be the setting on your thermostat.
Is your system set to Heat or Cool only? Check to see if the system is set on one or the other.
Setting your fan to “AUTO” will make the system heat and cool as needed. Some prefer to only have one and prevent running heat in the summer or A/c in the winter. With Auto, It only would turn on if your temperature hits the preset levels be in hot or cold.
One way to keep air always circulating is to set your fan to on. I do this year-round. Fans also have an auto setting, but for me, I find always on keeps all areas of the house more stable in temperature.
2. Dirty Air Filter
This is one of the big three main issues that homeowners may be able to do something about. Airflow return, Airflow supply, and Power.
Air filters need to be changed at least every three months. In some areas, it may end up as little as every month. If your filter is dirty and blocking airflow, your system cannot function. This can cause breakers to trip and the system to completely shut down.
When it comes to filters, use a quality filter, but not one that blocks too much airflow. Filters that brag about capturing everything impedes your air flow. Some systems are built for this, others end up starving for air.
If your air filter is clean, but you think it could still be causing the problem, see what happens if you run it with us for a half-hour. This could be a way to diagnose if your system i starving for air with the filter in. I don't recommend running your system for very long without a filter.
In the house I live in the HVAC was not getting enough return air from due to the size of the return grill being too small. The filter, the grill cover and the size of the opening all affect the amount of return air to the system. I had to have another return air added so now I have two filters to change.
Check your Supply Vents
Supply Vents being closed or covered can also cause the problem. A system that is not able to blow the air back out will start to heat up and eventually will give up altogether. HVAC systems are designed to have a minimum amount of air coming in and out. If you close to many vents than the air coming in can no loner get out.
To diagnose Supply Vent Issues
Just open all your vents and run the system. If you start to notice cool air blowing again then you solved the problem. Try not to close more than a vent or two at a time to prevent the problem from happening again. It's also possible that you don't have enough return vents and may need to get some added.
Check Your Circuit Breaker
This is common when your system is having problems especially due to something you caused. (like blocking is air supply)
Once you have checked the issues above and the system has air see if you can find any visible leaks. Visable leaking coolant requires an experts attention.
If your system has air and no visible leaks its time to check the power. You should have a break in the breaker panel, a breaker next to the outdoor unit, and a breaker in the inside unit. I would only recommend resetting them once if you find a breaker that has been tripped. If you reset the breaker and it trips again then most likely you are going to need expert assistance.
Refrigerant or coolant Leak
Most often you are not able to tell if the system has a coolant leak. Call your local HVAC technician do diagnose refrigerant issues.
4. Air Duct Leak
This could only cause a major problem is the main supply of air from your blower somehow came apart. Other than that leaks are an efficiency issue and if you have bad leaks you should get them fixed.
5. Dirty Evaporator Coils
Evaporator coils get dirty, this can affect the performance of your air conditioning system, if bad enough it can cause overheating and shutting off.