Chevrolet Brookwood Dome Light Bulb Size

Additional Notes

• The 211-2 is a festoon-type bulb measuring 41mm in length with an SV8.5 base, rated at 12 volts and 12 watts. Festoon bulbs are cylindrical in form and mount by pressing into spring clips at each end rather than twisting or pushing into a socket.
• The 1004 is a dual-filament bulb with a BAY15d bayonet base, rated at 12 volts with a 21/5W output. The dual-filament design means the bulb carries two separate circuits within a single envelope, each producing a different level of brightness.
• The 1004 is noted as a variant of the 1157. The 1157 and 1004 share the BAY15d bayonet base format, though they differ in their electrical ratings, which means the two types are not directly interchangeable despite their physical similarities.
• The Chevrolet Brookwood used the 1004 bulb for the dome light across the 1958-1960 model years, while the 211-2 festoon bulb was fitted in 1961 and again across the 1969-1972 model years.
• The shift from the 1004 to the 211-2 between the 1960 and 1961 model years represents a change in both base type and bulb format, from a bayonet-mounted dual-filament unit to a festoon single-filament unit. These two types are physically and electrically incompatible with each other.
• Both the 211-2 and the 1004 conform to ANSI standards recognized in the United States and Canada, placing them within a standardized North American bulb classification system.