AC Not Cooling After Circuit Board Replacement: Here's How to Fix

AC Not Cooling After Circuit Board Replacement: Here's How to Fix

An air conditioner circuit board is an essential component in the HVAC system because it regulates various operations of the system. However, if your AC still isn’t cooling after the replacement, the problem might not be the board itself. The problem may be in the installation process or in other components that are connected to it. No matter whether you are a homeowner who is trying to fix something on your own or a technician who has just completed an installation, it is crucial to know what to look for next. This article provides information on the causes of cooling problems after circuit board replacement and how to solve them.

Common Reasons Your AC Isn’t Cooling After Circuit Board Replacement and How to Fix Them

Here are the most common reasons your AC isn’t cooling after replacing the air conditioner circuit board, along with simple, effective fixes to help you get your system running properly again.

1. Wrong Circuit Board Installed

Not all control boards are universally compatible. Even boards that look identical can have different voltage ratings, relay types, or programming. An incompatible air conditioner circuit board may not communicate properly with your system.

How to fix:

• Check your AC unit’s model number and ensure it matches the board specifications.

• Check the compatibility of the part with the manufacturer’s documentation or the part database.

• If the wrong board was installed, it should be replaced with the right one to prevent further issues.

2. Wiring Connections Are Incorrect or Loose

When replacing the board, the wires may be misplaced or the connections may be left loose. This can assist in keeping vital components like the compressor or blower motor from receiving power.

How to fix:

• Turn off all power to the system.

• Use the unit’s wiring diagram to verify every connection to the air conditioner circuit board.

• Reconnect any loose or misplaced wires securely, paying close attention to R (power), Y (cooling), G (fan), and C (common) terminals.

3. Thermostat Not Communicating With the New Board

The thermostat sends the signal to cool. If it doesn’t communicate properly with the new board, the system won’t start even if everything else is working.

How to fix:

• Confirm the thermostat has power and displays correctly.

• Ensure all thermostat wires are securely connected, especially R and Y.

• Check the thermostat and reset or reprogram it if needed.

• For smart thermostats, look for firmware updates or perform a reset.

4. Indoor Blower or Outdoor Condenser Not Operating

Cooling requires both indoor and outdoor components to be active. You won't get cold air from the vents if either isn't functioning.

How to fix:

• Check breakers and fuses for the power supply to both components.

• Observe whether the blower fan and condenser fan turn on when cooling is activated.

• Test that each motor is receiving the correct voltage from the control board.

• If not, revisit wiring or inspect the board’s relay outputs.

5. Safety Switches or Sensors Are Tripped or Unconnected

HVAC systems include safety switches and sensors that can disable the cooling function if triggered. These may have been disconnected or overlooked during board replacement.

How to fix:

• Check for any blinking lights or codes on the control panel.

• Inspect float switches near the condensate line, high/low pressure switches, and limit switches.

• Ensure all safety switches are connected and functional. Reset only after resolving the underlying cause.

6. Compressor Not Starting Due to Faulty Capacitor or Contactor

If the compressor isn’t running, the system won’t cool, even with a functioning air conditioner circuit board. Common issues include a failed capacitor or contactor.

How to fix:

• Check for a click from the outdoor unit when cooling begins; this means the contactor is engaged.

• Use a multimeter to test the contactor and capacitor for correct operation.

• Replace the capacitor if it’s swollen or has failed its test.

• Make sure the contactor receives 24V from the board when cooling is activated.

  
  

7. Refrigerant or Airflow Issues

Electrical components may be fine, but low refrigerant or restricted airflow will prevent proper cooling.

How to fix:

• Look for ice buildup near the evaporator coil or on the refrigerant lines.

• Replace dirty air filters and ensure return air ducts are clear.

• If the refrigerant is low or if you think it is leaking, then you should consult a certified HVAC technician.

8. System Not Reset After Installation

Some systems require a full reset after a new board has been installed to bring it back to its default state and to ensure that it is in harmony with other parts.

How to fix:

• At the circuit breaker, cut off the electricity to the outdoor and indoor units.

• To make sure the system has been completely reset, turn off the power for five to ten minutes.

• Switch on the power, turn on the thermostat, and observe for normal functioning.

• Consult the new board’s installation manual for any required reset procedures or configuration settings.

Replacing the air conditioner circuit board is a key repair, but cooling issues can still occur. By checking common areas, you can often restore proper function without major repairs. If problems persist, contacting a licensed HVAC technician is the best next step to ensure your system runs efficiently.

Written by Allen Rode for PartsHnC, your trusted source for high-quality HVAC parts, including water heater components, air conditioner parts, and heat pump solutions.