Upon arrival, the unit had tripped due to a pressure switch fault. Upon inspection, I discovered that the pressure switch tube was clogged. I carefully blew out the tube, restoring the system's functionality. Next, I conducted a combustion analysis and found that the oxygen levels were low, indicating an early stage of failure in the secondary heat exchanger. To ensure the customer's safety, I confirmed that they had carbon dioxide alarms installed throughout the house. Finally, I placed an order for the necessary heat exchanger replacement parts.
