Upon arrival, I found the unit operational. The client reported that when the furnace fails to work, it displays a regular status code. I advised the client to contact us again if the issue recurs. To address the problem, I recommended installing a thermostat to help monitor and manage the furnace's performance more effectively. This should provide better insights into the system's status and potentially prevent future malfunctions. I ensured the client understood the importance of the thermostat in maintaining the furnace's efficiency and reliability.