Embodiments of the disclosure pertain to a method for monitoring a heat exchanger unit that may include the steps of: associating a monitoring module with an airflow side of the heat exchanger unit; operating the monitoring module whereby a microcontroller performs tasks related to data acquisition, data comparison, and providing an indication; and taking an action based on the indication. The monitoring module includes an at least one sensor proximate to the airflow side; a logic circuit in operable communication with the at least one sensor, and further comprising the microcontroller.