Chevrolet Chevelle Trunk Bulb Size

The Chevrolet Chevelle trunk utilizes a 1003 bulb size for the specific lighting component located within the rear storage compartment area. Data for the specified vehicle covers the period from 1964 through 1973.

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
1964-1973	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 Chevrolet Chevelle uses the 1003 bulb for trunk illumination across all listed model years, spanning 1964-1973.
The 1003 is an ANSI-standardized bulb type recognized in both the United States and Canada.
This bulb operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard automotive interior lighting of that era.
The 1003 is a single-filament bulb, meaning it serves one lighting function only and carries no secondary circuit for dimming or dual-intensity output.
It uses a BA15s bayonet base, a single-contact mount where the "s" denotes a single pin, distinguishing it from the dual-contact BA15d variant with which it is not interchangeable.
The BA15s base requires a quarter-turn insertion into a matching socket, a fitment method that differs from wedge-base bulbs and requires a socket specifically designed for bayonet-style mounting.
Because the 1003 shares the BA15s base with several other bulb types, substitution requires confirming that voltage and wattage ratings also match, as base compatibility alone does not guarantee a correct replacement.