Clock and Radio Stay On With Key Off - Power Antenna Backfeed

Electricalintermediate✓ OP Confirmed

Problem

Clock, radio, and super monitor stayed on with the ignition switch off. The radio ACC wire was receiving approximately 9 volts with the key off. The cigarette lighter power wire also had 9 volts constantly with the dome fuse in. Removing individual fuses (cigarette, dome, radio inside) did not fully resolve the issue - the super monitor would only turn off when the Radio No. 1 fuse was removed from the engine compartment fuse block.

Radio stays on with ignition offClock stays on with ignition offSuper monitor stays on with ignition off~9 volts present on ACC wire with key offCigarette lighter power wire has 9 volts constantlyContinuity between dome fuse circuit and cigarette fuse circuit where there should not be

Root Cause

Previous owner had incorrectly wired an aftermarket radio and rigged the power antenna to always turn on. The crossed wires caused battery constant power to backfeed into the ignition-switched circuit, keeping accessories powered with the key off. The ~9V (rather than full 12V) was a clue that current was flowing through electronics with semiconductors in the path, not a direct short.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted March 2020 on SupraForums.com