Which statement indicates a DC heater malfunction?

Which statement indicates a DC heater malfunction?

• A. 1 only
• B. 2 only
• C. Neither
• D. 1 and 2 Both

Answer: (D)

Two independent diagnostic signals are used to judge the DC heater’s condition. When both indicators show a fault, you have strong evidence that the heater system is malfunctioning because the chance that two separate monitors would falsely indicate a problem at the same time is low. Each signal could be affected by a sensor error or a transient fluctuation, but their agreement points to an actual issue with the heater or its control path.

In practice, this means you should treat the situation as a heater malfunction and proceed with safe shutdown and troubleshooting. Inspect the heater element and its power path for issues such as a open circuit or short, verify the control circuitry and sensors, check wiring and connectors, and measure relevant electrical values (like coil resistance and supply conditions) to pinpoint the fault. If only one indicator were abnormal, you’d need to investigate that single signal and its related circuit, but with both signaling a fault, the fault is considered confirmed rather than uncertain.