If the AC condenser outside is running but the indoor blower doesn't turn on, the problem might be with the control board. Different things can cause this problem, so an air conditioning repair technician has to rule out problems with the thermostat and other parts in addition to testing the control board. Here's how to tell if the control board is bad in your HVAC system so you can know what repairs your AC might need.
How To Tell If The AC Control Board Is Bad
The control board receives power from the main electrical line and then sends out power to various parts of the AC. For instance, when the thermostat triggers the blower, the control board sends power to the electronic parts that start the blower motor. When the control board is bad, the affected parts of your AC won't get power, so they won't operate. You can get hot quickly on a sweltering summer day, so a bad control board could need emergency repair.
An air conditioning repair technician can tell if the control board is bad by measuring the volts with a meter. First, incoming power is tested to make sure the control board is actually receiving the right amount of power. Next, power coming out of the control board is tested at various points to make sure the parts of your AC are receiving the right amount of power.
If the input power is correct, but the board isn't putting out enough power, then the control board is probably bad. However, the technician also has to check for things like bad wires and loose connections too.
Repairs Your Air Conditioner Might Need
If the repair technician determines the problem is with the control board and not other parts or wiring, then the board needs to be replaced. There are many wires that connect to an HVAC control board, so replacing a board is usually a job for a trained technician to ensure the electrical connections are hooked up properly and your AC operates safely.
If the control board seems to be putting out the right amount of power, the repair technician has to troubleshoot the other parts of the AC. The transformer or wiring might need to be replaced. The technician can use the multimeter to test the electronic components to find the one that's damaged and keeping your AC from running.
An AC control board can go bad because of an electrical problem such as a lightning strike, and the board can also go bad if your AC gets dusty and dirty inside. If dust caused the control board to overheat, the repair technician might need to clean your air handler in addition to replacing damaged parts so your air conditioner is ready to work properly again.