1979 Ford Bronco/F100-F350 Radio Circuit Troubleshooting & Wiring Diagram

This is page 34 of a Ford service/trouble-shooting reference covering the Radio circuit for 1979 Bronco and F100 through F350 trucks. The "How the Circuit Works" section explains that when the ignition switch is in RUN or ACCY, power travels through fuse 10 to the radio; AM and AM/FM monaural radios use a single dash-mounted speaker while the AM/FM multiplex radio has a speaker in each door. The Trouble-Shooting section provides step-by-step diagnostics: if there is no sound, verify the tuner is on a broadcast frequency, check the antenna lead, and check speaker connectors; if still inoperative, check fuse 10, power to fuse 10, and power at the radio connector (illustrated with a photo captioned "Checking For Power At Radio Connector"). Speaker circuit checks include continuity testing at speaker connections, verifying 2-4 ohm speaker resistance, and listening for a popping sound with a self-powered test light. Guidance is given for single and dual speaker system failures, ending with speaker replacement if all wiring checks pass. A partial wiring diagram shows the radio speaker circuit through connector C514, with branches for "Without CB Radio" and "With CB Radio" via a CB Radio Relay, using black (bk) and brown (br) wires.