Goodman Heat Pump Error Code A3

The A3 code indicates a fault with the outdoor coil temperature sensor. The control board has detected that the sensor circuit is shorted, open, disconnected, or producing a reading outside the expected range. This sensor is responsible for monitoring the outdoor heat exchanger coil temperature, which the system uses to manage defrost cycles and protect the equipment.

Running the unit with an active A3 fault is not recommended. The outdoor coil sensor directly controls defrost cycle timing, and without accurate sensor data the coil can accumulate ice, reducing efficiency and potentially overloading the compressor. Continued operation under these conditions can cause additional component failures that are more costly to repair.

A power reset may temporarily clear the A3 code, but if the underlying sensor fault is still present the code will return once the control board re-checks the sensor circuit. A reset is useful for confirming whether a fault is intermittent, but it does not repair a failed sensor, damaged wire, or bad connection. The root cause must be corrected for the fault to clear permanently.

A homeowner with basic comfort around electrical connections can check whether the sensor connector is loose or unplugged, which is the most common cause and requires no parts or tools beyond a visual inspection. If the connector is secure and the error persists, diagnosing a failed thermistor or damaged wire requires a multimeter to check resistance values, and replacing the sensor involves working inside the outdoor unit. If you are not comfortable with that level of work, a licensed HVAC technician should handle it.

If the fix is simply reseating a loose connector, there may be no parts cost, and a service call alone typically runs between 75 and 150 dollars depending on your area. Replacing the outdoor coil thermistor itself is a relatively inexpensive part, generally in the 20 to 60 dollar range, with total repair costs including labor often falling between 100 and 250 dollars. If the control board turns out to be the cause, board replacement is significantly more expensive, often ranging from 300 to 600 dollars or more with labor.