License Plate and Trunk Light

License Plate and Trunk Light

The Electrical rear lighting circuit on 1932-1972 Passenger, 1939-1970 Mercury, 1932-1979 Pick Up vehicles includes the license plate light and trunk light power integrated into the tail and body harness system. These circuits branch from the main lighting feed and rely on proper routing and grounding to maintain steady illumination. Unlike primary headlight circuits, license plate and trunk lighting are low-load branches, but they are vulnerable to corrosion, insulation breakdown, and poor grounding due to their rear body location.

This collection supports the wiring path serving those rear illumination points. Power routing is handled by the License Plate Light Wire and License Plate Light Extension Wire where additional length or routing changes are required. Combined circuits such as the License Plate Light & Gas Tank Sender Wire integrate rear lighting and sender feed within a shared harness section. At the light housing, License Plate Light Socket Wires and the Trunk Light Socket Wire complete the final connection between harness and bulb socket. These components restore continuity between the main rear harness and the individual light assemblies without altering the factory circuit layout.

Rear lighting circuits are simple, but they fail quietly and often go unnoticed until inspection.

Technical & Fitment

The license plate light receives power when the headlight switch activates the tail light circuit. Voltage travels through the rear body harness and into the License Plate Light Wire or integrated License Plate Light & Gas Tank Sender Wire, depending on model configuration. Any resistance at splice points or brittle insulation near the trunk hinge area will reduce output or create intermittent operation.

The trunk light circuit operates independently of brake and tail light loads but shares routing paths in many applications. The Trunk Light Socket Wire must maintain a clean ground and secure terminal fit to prevent flicker when the deck lid moves. Extension sections such as the License Plate Light Extension Wire are commonly replaced during restoration due to cracked insulation or prior repairs.

Fitment will vary by model year or body harness configuration.

Examine rear harness routing and socket connections before replacing bulbs for low output concerns.