Final answer:
A growler is a tool used to diagnose the condition of a car's starter armature by inducing vibrations and detecting potential shorts in the windings.
Step-by-step explanation:
A growler is an electrical device used to test the condition of a starter's armature in automotive repair. When troubleshooting a starter motor, it is important to determine if the armature has shorts, opens, or grounds. The growler operates by creating a strong magnetic field that induces vibrations in the armature windings, which can be detected by a metal strip or hacksaw blade held above the armature. If the blade vibrates while over a particular segment of the armature, this indicates a short. The growler test is a practical and common method used in auto repair shops for diagnosing starter problems.