Heat Controller Air Conditioner Error Code 44

Error code 44 indicates an open or short circuit fault in the outdoor air thermistor sensor. This sensor monitors the ambient outdoor temperature and feeds that data to the control board. When the sensor signal reads 0 volts (short) or 5 volts DC (open) instead of the normal 2.5 volts DC at room temperature, the unit triggers code 44 and shuts down.

It is not recommended to continue running the unit with code 44 active. The control board uses outdoor air temperature data to manage compressor cycling and defrost timing, and operating without an accurate sensor signal can lead to improper operation or component stress. The unit will typically shut itself down when this code appears as a protective measure.

Resetting the unit by cycling power may temporarily clear the fault display, but code 44 will return as soon as the control board reads an abnormal signal from the outdoor thermistor again. The underlying cause, whether a failed sensor, damaged wiring, or a loose connector, must be identified and corrected for the error to clear permanently.

A knowledgeable DIYer can perform basic diagnostics by unplugging the thermistor and measuring its resistance with a multimeter. A reading close to 10 kilohms at 25 degrees Celsius (77 degrees Fahrenheit) suggests the sensor is good and the wiring or control board should be investigated further. Replacing the thermistor itself is a relatively straightforward repair, but diagnosing control board issues is best left to a qualified technician.

If only the thermistor sensor needs replacement, parts typically cost between $10 and $40, with labor bringing the total repair to roughly $75 to $200 depending on your area. If the control board is at fault, costs can range from $150 to $500 or more including parts and labor. Getting a diagnosis before authorizing parts replacement helps avoid unnecessary expenses.