Ford TFI E-Core Ignition Coil Test Light Diagnosis - Coil Negative TACH Lead

This document is a single illustrated service procedure (figure 7.3) showing how to perform an initial diagnosis of a Ford TFI (Thick Film Ignition) E-core ignition coil using a 12-volt test light. The line drawing depicts an E-core coil with its connector, a 12-volt test light with its probe touching the coil's negative (TACH) lead terminal, and the test light's clip lead connected to an engine ground point. The caption instructs the technician to connect the test light to the coil negative (TACH) lead, ground the other end of the light, crank the engine, and observe the light: it should flash as the ignition primary circuit alternately grounds and opens. A flashing light indicates the ignition module is switching the coil primary circuit properly; no flash would point to a primary-side problem. The document contains no year, model, engine, or part-number information itself, it is a generic ignition diagnostic figure, uploaded as part of a set of ignition-related reference scans for a 1990 Ford Bronco, which uses the TFI ignition system this test applies to. It pairs with companion scans covering coil primary resistance, secondary resistance, and supply voltage tests.