When your air conditioner stops working, you're likely going to call an air conditioning repair service to fix it. However, some problems are easy to solve by yourself. Here are a few issues that can be resolved with DIY repairs.
Most thermostat problems can easily be fixed on your own with a little bit of investigation. When you suspect that the issue is due to the thermostat, state by changing the batteries. You may be seeing numbers on the digital screen, but that doesn't mean the thermostat is accurately reporting them.
There may also be a simple case of user error. Make sure that you check your schedule and fully understand what the thermostat is supposed to do. For example, when the warm weather started, you may have forgotten to change your thermostat from heating to cooling mode. If so, a thermostat set to 66 degrees will only turn the heat on if the temperature drops, not cool down your home if it gets too hot.
You may have noticed that the condenser coil inside the air handler unit has frozen up. This is a big reason for concern, but may be caused by a dirty air filter. If the cool air is trapped in the air handler and cannot make it to the vents, it is going to cause the temperature in the air handler to drop. Coils can freeze, and the air conditioner will no longer be able to extract heat from the air. It results in your air conditioner shutting down due to refrigerant not being able to make its way through the system.
The best thing you can do to fix this is to turn your air conditioner off and let the coils naturally defrost on their own. You can speed it up with a hairdryer, but don't try to chip the ice off the coils. Then replace the air filter with a brand new one, and turn the unit back on. Hopefully, this will prevent the temperature dropping to a point where the coils freeze again.
If this doesn't solve the problem, you'll need to bring in a professional. Frozen coils can be caused by a refrigerant leak that needs to be fixed or a lack of refrigerant in the system. Both of these problems will require some special tools that you don't have access to and don't know how to use on your own.