In order to reduce the amount of electricity that an air conditioner uses, AC designers will use a motor that is just strong enough to keep a fan running once is has started but is not strong enough to start the fan in the first place. To provide the initial burst of power needed to start the fan, they will then insert a capacitor into the system. While this design works most of the time, it will leave your system crippled if the capacitor goes bad. To diagnose the problem and cope with it until a HVAC technician gets there, you need to know how a capacitor works.
What Is a Capacitor?
A capacitor is a small metal canister that looks much like a tiny pop can. Wires connect the capacitor to the fan's circuit board. When power flows through the board, the capacitor will absorb electricity until it is full. Then when there is a draw on the system, such as when the fan starts, the capacitor releases its stores to provide a boost in electricity. When you look for a blown capacitor, you look for a canister with bulges in it and/or a brownish fluid leaking out.
Diagnosing a Blown Capacitor
To confirm that your unit has a blown capacitor, you can either remove the cover that protects the electrical components of your condenser unit and then look for the capacitors, or you can do the following:
1. When your fan is on and your evaporator unit inside your home is running, grab a long-necked screwdriver and go out to your yard.
2. Reach through the protective grid that protects your condenser unit and give the fan blade a good push. Make sure you quickly remove the screwdriver to avoid damage.
3. If the fan keeps running once it starts, then you have a blown capacitor.
*Remember that your system will only operate until it reaches the desired temperature programmed into your thermostat, at which point it will shut off, and your fan will be unable to start again. Thus, kickstarting your fan is only a temporary solution to keep your system limping along until you can have it repaired.
Capacitors tend to go bad when the load on your system is at its highest—in other words, when it is really hot outside. Thus, capacitors can cause your system to fail when you need it the most. As soon as you know what the problem is, you should call for a repair, such as from Stone Heating And Air, to get your system running properly as soon as possible. However, you can start your condenser fan as needed using the method described above and provide some cooling to your home while you are waiting.