WARNING: Working with household electrical systems can be dangerous. If you're not comfortable working with electricity, call a qualified HVAC technician. Incorrectly diagnosing or repairing an electrical fault can lead to serious injury or even death.
1. Check the Simple Stuff First:
* Thermostat: Make sure the thermostat is set to "Cool," the temperature is set lower than the current room temperature, and the system is not in "Fan Only" mode. Try switching the thermostat completely off and then back on again. Sometimes a simple reset helps.
* Power Supply: Confirm that the breaker controlling your AC unit hasn't tripped in your breaker box. Reset it if it has tripped. Also check for any loose connections at the breaker or the main electrical panel. Sometimes an overloaded circuit can cause the breaker to trip.
* Circuit Breaker: If the circuit breaker trips immediately when you reset it, there's a serious problem that needs immediate professional attention. Do not attempt to re-enable the breaker in that case.
2. More Advanced Checks (ONLY IF YOU ARE COMFORTABLE WORKING WITH ELECTRICITY):
* Capacitor: The AC compressor often has a capacitor (a cylindrical component usually near the compressor motor) that stores energy to help the motor start. A faulty capacitor can prevent the compressor from turning on. WARNING: Capacitors can hold a dangerous electrical charge even when disconnected. Discharge the capacitor completely before handling it (using a capacitor discharge tool or a insulated screwdriver to short the terminals). Visually inspect the capacitor for bulges, leaks, or burn marks. If it looks damaged, it likely needs replacement; however, this requires specialized tools and knowledge to safely replace, calling in professional is highly advised.
* Start Relay: The start relay is a small electrical switch that helps the compressor start. A faulty start relay can prevent the compressor from engaging. You may need to access this relay. This will require expertise to both locate and test. It can be tricky to test the relay properly; an ohm meter is normally necessary. A multimeter should be used on the relay to test continuity.
* Compressor Overload Protector: Some systems have an overload protector that will cut power to the compressor if it overheats. Check the manufacturer's instructions for how to reset it if it is tripped.
* Condenser Fan Motor: Make sure that the condenser fan (outside unit) is spinning freely; if the fan is obstructed or seized it can cause problems to the compressor.
3. Checking Voltage (Requires a Multimeter):
* Power at the Compressor: With the power OFF at the breaker, carefully disconnect the wires to the compressor and then turn the power back ON. Use a multimeter to check the voltage at the compressor terminals. You should see 240V (in most areas). If the voltage isn't present or incorrect, there's a problem in the wiring, at the breaker, or with the contactor/relay. DO NOT attempt to measure voltage while the power is on, you risk serious electric shock.
* Checking the contactor coil: With the AC turned on, check the voltage across the contactor coil(s). If there is no voltage, you may have a wiring problem or a problem with the control circuit.
4. When to Call a Professional:
If you've checked the simple things and aren't comfortable with the more advanced checks, call a qualified HVAC technician. Trying to diagnose and repair electrical problems without the proper knowledge and tools can be extremely dangerous. A technician has the necessary training and tools to safely and effectively diagnose and repair the problem.
Remember: Safety is paramount. If you're not comfortable working with electricity, don't hesitate to call a professional. The cost of a repair is much less than the cost of a serious injury.
