Upon arrival, I assessed the situation and found that the power was off and the thermostat was not maintaining the desired temperature settings. After a thorough inspection, it became clear that the thermostat was malfunctioning. I proceeded to replace the faulty thermostat with a new one, ensuring compatibility with the existing system. Post-installation, I calibrated the new thermostat to the customer's preferred settings. Following this, I tested the system to confirm that it was operating correctly and efficiently. The power was restored, and the thermostat now accurately holds the set temperature, ensuring optimal comfort and energy efficiency.