There are several very easy ways to diagnose a broken AC or Heater. Before you do this, however, you need to make sure you know what you are looking at. You dont want to look up items related to motorcycles if you are looking at cars right? So lets go over the types of Residential HVAC systems you will see in Texas. Do not worry, there are very few.
1) The first system is called a 3 piece system. This has an outside AC condenser, an inside Evaporator Coil with attached Furnace. Its called a furnace because it uses gas and flames for heat.
2) The second system type is a two piece system called a Heat Pump system. These are sued where there is no gas available in the neighborhood or the builder simply didn't want to bring gas in. This consists of an outdoor AC condenser and an indoor Air Handler. Where does the heat come from? It comes from the AC condenser which actually has a reversing valve so that instead of cooling the house and heating the outside like it does in summer it is heating the inside and cooling the outside. (This is a very layman way of describing what a Heat Pump does. A Heat Pump is an engineering marvel so I dont mean to over simplify but this blog is for the average homeowner)
3) This third and last type is a two piece system and has an outside AC condenser and in indoor Air Handler. The heat comes from little toaster strips inside the Air Handler. They are called heating elements and they look just like what's in a toaster give or take (most are actual coils).
Now that you know the types here is how you see what you have. Very easy. Do you have gas at your house? For example do you have a gas stove and a gas water heater? If you answered yes than there is a 98% chance that you have a gas furnace and are System #1 that we spoke about. If you dont have gas then how will you know if you have #2 or #3 since they are so similar? Easy, just go outside to your AC condenser, the big AC equipment outside that you hear running all summer long. This is usually on the side of your house. Look down inside. If you see a whole bunch of parts (more than 2) then you have a Heat Pump. Heat Pumps have lots of parts whereas in a conventional AC condenser you will just see this big black thing called a compressor with a couple copper pipes hooked to it.
Now that you know your system here is how to easily diagnose. Ask yourself the following questions and read the answers.This is for diagnosing Air Conditioning. The next set will diagnose heating problems.
1) Is the system blowing air inside your house? I am not asking if its cold or hot air, I am just asking if it is blowing any air at all. IF you say "Yeah its blowing air, but its not cold" then that's okay we will get to that. When a system is blowing air that tells us that the indoor portion of the equipment is doing its job. It does not care if it is blowing over something hot or something cold, it just does what its told. When you tell the Thermostat to cool your house it sends a command to the unit in your attic or closet. That command simply says "blow air please". The system doesnt know its blowing cold or hot, it just spins a blower motor attached to a wheel and blows air. So if this is blowing air in the house then we know all of our issues are outside at the AC condenser. See #3. If not blowing air see #2
2) If the system is not blowing air then all of our issues are related to the inside equipment. First thing we have to do is make sure the system is getting power. Go check your breaker panel in the garage. You are looking for the breaker labeled 'furnace' or 'heat' or 'Air Handler'. You do not want the AC breaker, that is for outside and we are dealing with inside. Go ahead and cycle the breaker by turning it off all the way and then back to ON. Hopefully nothing tripped when you did. If the breaker immediately trips or was already tripped when you go there then call a service company. This is not something you will be fixing yourself because there is a major electrical short. But if they look fine and good then go to your thermostat and make sure the display is working. If not then check the batteries and try again. If the display works with new batteries then you probably fixed your problem. Please do not think that a thermostat solves everything. For some reason it is the first thing homeowners go to Home Depot and replace. usually when they do they wire it wrong and it did not fix the original problem so they put the old one back on wiring it wrong again. Once you verified that the thermostat is working then try different settings like FAN-ON. If it comes on when you tell it to but not when its in AUTO mode then there is most likely a limit Fault in the furnace. For Air Handlers this will be a bad fan relay board. Again, call a repair company