So, this is really a loaded question because there are many things that can cause your system not to cool. Rather than boring you with all the potential issues that could lead you down a rabbit hole, I figured I would provide some basic things to check before calling an HVAC company.
The key thing to identify here is what type of system you have. The most common system used in Jacksonville, Florida, is a split-system heat pump.
A split system means that you have an indoor unit commonly referred to as an air handler or an electric furnace. This unit is usually located in a closet, garage, utility room, or even your attic and, in some rare cases, under the home. The other component is located outside and is commonly referred to as the condenser.
You might also have a packaged unit. This means you have both your air handler and condenser housed together in one package outside the home. These are commonly seen on manufactured homes, some historic homes that never had AC before, and mobile homes.
There are other types of systems, such as gas furnaces and water-to-air-source heat pumps. These are not as commonly used, and for this FAQ, I’ll stick to the most commonly used equipment.
Now that we have that out of the way, let’s dive into split systems. Split systems should be running on dedicated circuits coming from your breaker panel. This means you should have two breakers in the panel that supply 240V to the system components (the air handler and the condenser). Each breaker should be labelled in the panel. The air handler breaker should be labelled HEAT, AHU, or sometimes FURN. The other breaker should be labelled ‘AC’ or sometimes HP or CDU.
Now diagnostics time.
- Are both breakers in the “ON” position? If yes, move to Step 2. A tripped breaker may appear to be in the middle position or, in some cases, may appear to be on. If a breaker has tripped, you must turn it all the way off and then turn it back on again. If no, reset the breaker and see what happens. If the breaker trips immediately, you may have a high-voltage short somewhere in that circuit, and you should call an HVAC company to determine where the short is located. Buyer beware: Untrustworthy technicians may try to persuade you to replace your entire system. Pay attention to what they are doing during the diagnostic process, and ask them to show you how they reached their conclusion. An experienced technician should be able to demonstrate the issue and explain it in a way that is easy to understand. If they can’t explain it, they may not understand the problem, or they may be more concerned with making a commission from the sale of a new HVAC system.
- Is there power at the thermostat? If yes, move to Step 3. If your breakers are on, you should have power at the thermostat unless your thermostat requires batteries to operate. To eliminate the batteries as a potential issue, replace them with fresh batteries. The batteries should be located behind the faceplate. Each thermostat is different, so be gentle when removing the faceplate from the backplate.
- Have you checked your drain line? Your air handler should be equipped with a float switch and a cleanout T. The float switch should be located next to the drain line. You should see a device that resembles a small cup with a black wire coming out of the top. This is the float switch. Remove the top where the wire comes up and check to see if there is water inside. If there is, it means your drain line is restricted or clogged. If no, move to the next step. If yes, then you have a maintenance-related issue on your hands, and you’ll need to clean the drain line. The best way to do this is with a shop wet/dry vacuum cleaner. See “Drain Line Cleaning…” for more information.
- Is there water in the drain pan? If no, move to the next step. Some systems will have a secondary drain pan located under the air handler. This is common for air handlers located in the attic, on the second floor, or, in some cases, suspended in the garage. This doesn’t mean that if your unit is not in one of these locations, you don’t have a secondary drain pan or that you necessarily need one. Sometimes installers add them as a backup even when they are not required by code, while other times they don’t. If you have a secondary drain pan, you should also see another float switch. This one may look a little different. The easiest way to locate this switch is to find the wires coming from the pan to the inside of the air handler. If there is water in the pan, the float switch will be triggered, preventing the system from flooding the home. Usually, when water makes its way into the secondary drain pan, there is an underlying reason. Here are a few reasons why water might be there:
- Frozen evaporator coil
- Faulty primary float switch or incorrectly wired
- Clogged primary drain line
- Dirty Air filter caused icing
- Cracked Primary Drain Pan
- Air Handler not level or pitched
- Dirty evaporator coil
- Is the indoor unit running? If yes, move to the next step. If not, it’s recommended that you call an HVAC professional. However, you could try replacing the thermostat first to see if that resolves the problem. Remember to follow all instructions and turn off the power before replacing the thermostat. You’ll also need to configure the thermostat for a heat pump.
Is the outdoor unit running? If the indoor unit is running, that tells us that we have power and that the thermostat should be sending a signal outside to turn on. Sometimes the outdoor unit will appear to be running because the fan is spinning, but the compressor may not be or vice versa. If it’s making noises, it’s helpful to record a quick video of the system making those noises. Turn the AC breaker off for ½ hour or so, then turn it back on (record this by video) and see what happens. Whether the system comes back on or not, you should still call a professional to solve this problem. There are too many potential things that would interrupt operation to name, and most of it would require specific tools. The most common interruption for an outdoor unit not running is a failed capacitor. This is a cheap part that can be purchased online if you’re inclined to do so. The average capacitor replacement cost in the Jacksonville, FL market ranges from $250 to $800. Most AC companies won’t install your part, nor will they base their diagnostics off what you have done already. So if you’re inclined to do the work and diagnose it yourself, be prepared for that. You will need to collect info from your system so that you can buy the correct size capacitor. Then all you need to do is follow the schematics to ensure the capacitor gets wired up correctly. Be aware that improper wiring can and will cause permanent damage to your HVAC system and will VOID any warranties you may have with your installing contractor/builder and manufacturer.