ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsMedium
A client complains that their vehicle's interior dome light does not turn on when any door is opened, but it works when manually switched to the 'ON' position. All other interior lights function correctly. Which of the following is the MOST likely cause?
- AA blown fuse for the interior lighting circuit.
- BA short circuit in the dome light wiring.
- CA faulty dome light bulb.
- DA problem with the door jamb switch(es).
Show answer & explanationAnswer & explanation
Correct answer: D. A problem with the door jamb switch(es).
If the dome light works when manually switched on, the bulb, fuse, and main wiring to the light are functional. The issue is specifically with the automatic activation when a door opens, which is controlled by the door jamb switches. If one or more of these switches are faulty or disconnected, the 'door open' signal will not reach the light circuit.
Why the other options are wrong
- A. If the fuse were blown, the light would not work in any position, including manual 'ON'.
- B. A short circuit would likely cause the fuse to blow or the light to stay on constantly, not prevent it from coming on when the door is opened while allowing manual operation.
- C. If the bulb were faulty, it would not illuminate in any position, including manual 'ON'.
Dome Light Operation
Dome lights typically have multiple modes: OFF, ON (manual), and DOOR (automatic activation via door switches).
- Manual ON bypasses the door switch circuit.
- Door jamb switches complete a ground or send a signal when a door is opened.
- A fault only in the DOOR mode points to the door switch or its associated wiring.
Memory trick: Manual works, door fails, switch unveils.