Chevrolet Brookwood Courtesy Bulb Size

The Chevrolet Brookwood courtesy light utilizes bulb size 89 and bulb size 631 for interior illumination across various production periods. Data for the specific lighting components covers the period from 1958 through 1972.

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
1972	89
1969-1971	631
1958-1961	89

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	89
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	631

Other Locations

Additional Notes

The 89 and 631 bulb types cover all listed courtesy bulb applications for the Chevrolet Brookwood across the 1958-1972 model years represented in the specifications.
Both the 89 and 631 are ANSI-standardized single-filament bulbs sharing the BA15s bayonet base, which is a single-contact base with a 15mm collar and two retaining pins positioned symmetrically.
Despite sharing the same BA15s base type, the 89 and 631 differ in wattage: the 89 operates at 13W while the 631 operates at 21W, both on a 12V system.
The 89 is described as a lower wattage variant of the 1156, and the 631 is described as a variant of the 1156, meaning the 1156 family serves as the reference point for both bulb types.
The Chevrolet Brookwood used the 631 bulb for courtesy lighting across the 1969-1971 model years, while the 89 bulb was specified for 1958-1961 and again for 1972.
The wattage difference between the two bulb types means they are not interchangeable without consequence, as substituting the 631 for the 89 would introduce a higher current draw into the courtesy light circuit.