ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsEasy
A client complains that their vehicle's interior dome light does not turn on when any door is opened, but it *does* turn on when the dome light switch is manually activated. What is the MOST likely cause?
- AAn open circuit in the dome light's manual power supply
- BA short circuit in the vehicle's accessory power outlet
- CA burned-out dome light bulb
- DA faulty door jamb switch
Show answer & explanationAnswer & explanation
Correct answer: D. A faulty door jamb switch
If the dome light works when manually activated, the bulb and its main power supply are good. The issue is with the circuit that activates the light when a door opens. This circuit relies on the door jamb switch to complete the ground path, so a faulty switch would prevent automatic activation.
Why the other options are wrong
- A. An open circuit in the manual power supply would prevent manual activation, which contradicts the symptom description.
- B. A short circuit in an accessory power outlet would likely blow a fuse or affect other accessories, not specifically the dome light's door-activated function.
- C. If the bulb was burned out, the light would not turn on even with manual activation.
Dome Light Door Activation
Dome lights typically activate when a door is opened by a door jamb switch completing a ground circuit, allowing current to flow to the bulb.
- Two activation methods: manual and door-triggered.
- Door-triggered relies on door jamb switch.
- Manual activation bypasses door switch circuit.
Memory trick: Dome Light: Manual OK, Door Not? Jamb Switch Got Caught!