ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsHard
A vehicle experiences a complete loss of all electrical power immediately after a battery replacement. The new battery was installed correctly, and its voltage measures 12.6V. What is the MOST likely cause?
- AA faulty ignition switch
- BThe alternator is not charging the battery
- CA blown main fuse or fusible link
- DA short circuit in the starter motor
Show answer & explanationAnswer & explanation
Correct answer: C. A blown main fuse or fusible link
A complete loss of all electrical power after a battery replacement, especially if the new battery is fully charged, strongly suggests a break in the main power supply path from the battery. This is typically protected by a main fuse or fusible link, which can blow if there was a momentary short during installation or if the terminals were briefly reversed.
Why the other options are wrong
- A. A faulty ignition switch would prevent the engine from starting or accessories from working when the key is turned, but usually wouldn't cause a complete loss of *all* electrical power (e.g., dome lights, hazard lights) with the key off.
- B. The alternator not charging the battery would lead to a dead battery over time, but not an immediate, complete loss of power after a new, charged battery is installed.
- D. A short in the starter motor would primarily affect starting, and might drain the battery, but wouldn't cause a complete loss of all power immediately after battery installation if the main circuit is otherwise intact.
Main Fuse/Fusible Link
Main fuses or fusible links protect the entire vehicle's electrical system from catastrophic overcurrent, often blowing due to installation errors or short circuits, resulting in a complete loss of power.
- Protects main power circuit.
- Designed to blow under extreme load/short.
- Failure causes total power loss.
Memory trick: No Power At All? Check the Main Fuse Call!