Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsGeneral Electrical/Electronic System DiagnosisEasy
A client complains that their vehicle's interior dome light does not turn off, even when all doors are closed and the ignition is off. A technician observes that the dome light remains illuminated. Which of the following is the MOST likely cause?
- AA stuck door jamb switch.
- BA faulty dome light bulb.
- CAn open circuit in the dome light's power supply.
- DA short to ground in the dome light's wiring.
Show answer & explanationAnswer & explanation
Correct answer: A. A stuck door jamb switch.
If the dome light remains on when it should be off, it indicates that the control circuit is still completing the path for current. A stuck door jamb switch would signal to the Body Control Module (BCM) or directly to the light that a door is open, keeping the light on.
Why the other options are wrong
- B. A faulty bulb would prevent the light from turning on at all, not cause it to stay on.
- C. An open circuit in the power supply would prevent the light from ever turning on.
- D. A short to ground in the dome light's wiring would typically cause the fuse to blow or the light to always be on if it bypassed the switch.
Door Jamb Switch
A switch, typically located in the door frame, that detects if a door is open or closed, often controlling interior lights or door ajar warnings.
- Usually a normally closed switch that opens when the door closes.
- Provides a ground or signal to the body control module (BCM).
- A stuck switch can lead to lights staying on or not turning on.
Memory trick: The dome light's always on, like a never-ending party, because a door switch is stuck in 'open' mode.