Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsLighting Systems Diagnosis and RepairEasy
A vehicle's interior dome light does not illuminate when any door is opened, nor when the manual override switch is pressed. All other interior lights (dash, glove box) function correctly. Which of the following should the technician check first?
- AThe fuse for the dome light circuit
- BThe door jamb switches
- CThe vehicle's body control module (BCM)
- DThe dome light bulb
Show answer & explanationAnswer & explanation
Correct answer: A. The fuse for the dome light circuit
Since the dome light fails to operate regardless of door position or manual switch activation, and other interior lights are working, the most common and easiest-to-check single point of failure for the dome light is its fuse.
Why the other options are wrong
- B. If only door activation failed, door jamb switches would be suspect, but failure with the manual switch also indicates a broader issue.
- C. The BCM controls many functions, but checking the fuse is a simpler and more likely cause for a single non-functioning light across all activation methods.
- D. While a burnt bulb is possible, the 'neither door nor manual' scenario suggests a lack of power to the bulb rather than just the bulb itself. The fuse is a more fundamental check.
Fuse First Rule
When a single electrical component or circuit fails completely across all activation methods, check its fuse first.
- Fuses protect circuits from overcurrent.
- A blown fuse indicates an open circuit, preventing power flow.
- Easy and quick to diagnose with a test light or multimeter.
Memory trick: No light, fuse might!