Lennox Air Conditioner Error Code E416

E416 indicates that the outdoor coil temperature sensor has malfunctioned. The sensor may be open, shorted, or reading a resistance value outside the expected range. Because the control board cannot trust the sensor data, it disables the defrost cycle to prevent improper operation.

A reset may temporarily clear the fault code, but if the underlying sensor or wiring problem still exists, E416 will return as soon as the control board attempts to read the sensor again. The root cause must be addressed to permanently clear the code and restore defrost operation.

Repair costs depend on the specific failure. A coil sensor replacement is generally a lower-cost repair, typically in the range of $75 to $200 including parts and labor. If the outdoor control board is at fault, costs can range from $300 to $600 or more depending on the model. Diagnostic service calls are usually additional and vary by region.

Some steps, such as visually inspecting wiring and reseating a dislodged sensor, can be done by a knowledgeable DIYer. However, accurately diagnosing the fault requires a multimeter and the specific temperature-resistance chart for your coil sensor model. Replacing the sensor or control board typically requires a technician familiar with Lennox systems.

The system may continue to run in cooling mode without immediate risk, but in heating mode the disabled defrost function can allow frost to accumulate heavily on the outdoor coil. Severe frost buildup can restrict airflow and reduce efficiency significantly, and prolonged operation in this condition can stress the compressor. It is best to address the fault promptly, especially during cold weather.