Chevrolet El Camino Trunk Bulb Size

The Chevrolet El Camino trunk light requires a bulb size of 1003 for the specific lighting application. Data for the bulb specifications covers the range from 1959 to 1960.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1959-1960	1003

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1003

Other Locations

Additional Notes

The 1003 bulb follows the ANSI standard recognized in both the United States and Canada, making it a regionally standardized component rather than a proprietary specification.
The 1003 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament types that handle two functions such as running and brake light duties simultaneously.
The 1003 operates at 12 volts and draws 21 watts, placing it in a range typical of low-demand interior and auxiliary lighting applications.
The BA15s bayonet base on the 1003 features a single contact pin, which is a key fitment detail. A BA15d base, which carries two offset pins, is not interchangeable with the BA15s even though the physical housing may appear similar.
The Chevrolet El Camino used the 1003 bulb for trunk lighting across both the 1959-1960 model years, indicating a consistent specification across that production span.