Select the best answer for the question.
Two technicians are discussing stepper motor fuel gauges. Technician A says that a defective gauge can usually be repaired individually without replacing the entire cluster of panel gauges. Technician B says that if the power lead to the fuel tank sending unit is disconnected from the tank unit and grounded (ignition on), the fuel gauge should go to full.
Which technician is correct?
A. Neither Technician A nor Technician B
B. Both Technician A and Technician B
C. Technician A only
D. Technician B only
The correct answer and explanation is:
The correct answer is D. Technician B only.
Technician B is correct because, when the power lead to the fuel tank sending unit is disconnected and grounded while the ignition is on, the fuel gauge should indeed go to full. This is because the grounding of the power lead simulates the condition where the sending unit is indicating a full tank. The sending unit typically operates by varying its resistance based on the amount of fuel in the tank. When disconnected and grounded, the circuit is completed as though the tank is full, causing the gauge to read full.
Technician A’s statement is not entirely correct because fuel gauges, especially stepper motor-based ones, are often integrated into a cluster with multiple gauges. While it may be possible to repair a defective gauge, it is more common that a malfunctioning gauge within a cluster would require the replacement of the entire cluster. This is because modern vehicles often use a complex system where multiple components, such as stepper motors, are tightly integrated. Attempting to repair one gauge without replacing the whole assembly can lead to issues with calibration, performance, or continued failure of the gauge.
Thus, Technician B’s understanding of how grounding the power lead works is accurate in this context, while Technician A’s approach overlooks the complexity of modern gauge clusters.