What type of combustion problem can arise from a malfunctioning cad cell?

A malfunctioning cad cell, also known as a cadmium sulfide photoresistor, plays a crucial role in monitoring the presence of a flame in an oil burner. When the cad cell fails, it cannot detect whether the flame is present or not. This can lead to several operational issues, the most critical being failed ignition sequences.

When the cad cell cannot accurately sense the flame, the burner control system may not receive the necessary signals to continue operation. As a result, if the flame goes out or does not ignite properly, the control system may shut off the fuel supply, leading to failed attempts at ignition. This can create a cycle where the burner tries to ignite, fails, and shuts down, causing inefficiencies, potential safety risks, and an inability to maintain proper heating in the system.

The other options present possible issues in an HVAC system, but they don't directly stem from the malfunction of the cad cell in the same manner. Frequent overheating typically relates to issues with the thermostat, excessive carbon buildup often results from improper combustion or airflow, and inaccurate fuel measurements generally link to problems with the fuel delivery system rather than the flame detection mechanism. Thus, recognizing the importance of the cad cell in ignition sequences is key to understanding its role in the safe