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Understanding AC Control Board Failures

Most modern HVAC systems consist of numerous components that need to work together to heat or cool your home. Your air conditioner uses a compressor to drive its refrigerant cycle, allowing the evaporator to absorb warm air from your home. However, this side of your system must coordinate with the blower motor that distributes chilled air through your ductwork.

The control board provides this control and coordination. Understanding how your air conditioner's control board works can help you spot potential issues and recognize when your home's cooling system is suffering from a control board failure.

The Role of Your Air Conditioner's Control Board

Several things need to happen before your air conditioner kicks on and starts sending cold air through your vents. The thermostat acts as the eyes and ears of the system. You choose a setpoint on the thermostat, and a temperature element begins monitoring the environment. The thermostat will call for cooling if the ambient temperature goes above your setpoint.

When your thermostat makes this call, it signals to the air conditioner's control board to start the compressor. The control board relays this low voltage signal to your outdoor condenser unit's contactor. The contactor acts as a relay, using the low voltage signal from the control board to switch high voltage power to the compressor and condenser fan.

Meanwhile, the control board also switches power to your house blower fan, usually after a short delay, to allow the evaporator coils to cool. Depending on your air conditioner's model and overall sophistication, it may run through a few safety checks (including checking pressure switches) before engaging the compressor.

How a Failed Control Board Affects Your Home's AC

The control board takes input from house power and your thermostats and sends output to the condenser unit and blower motor. As a result, a faulty control board can interrupt the cooling path by not sending a low voltage signal to the compressor or failing to switch power on for the house blower. The board can also fail in a way that prevents the compressor or blower from shutting down.

While HVAC control boards are relatively simple compared to the circuits found in sophisticated computers, they still require care and experience to diagnose correctly. HVAC technicians need to confirm that the board is receiving the proper signals and that these signals are reaching their destinations. They must also check for wiring issues that might be interrupting these signals.

Unfortunately, there's no single set of symptoms that indicate a control board failure. If your air conditioner is operating strangely, remaining on for too long, or failing to shut off, any of these may indicate a problem with the control board. A trained HVAC technician can diagnose the problem for you and help narrow the issue down to the control board or another component.

Contact a company like Eco Green Home for more information.