Chevrolet Biscayne Automatic Transmission Indicator Bulb Size

Additional Notes

• The Chevrolet Biscayne automatic transmission indicator used six distinct bulb types across its 1960-1972 model years: the 53, 57, 194, 257, 1445, and 1895.
• The 1895 is the most frequently specified bulb across this application, appearing in the 1964-1967, 1969, and 1970 model years. It is a T5 miniature wedge bulb rated at 12V and 0.9W under the ANSI standard.
• The 194 bulb, used in the 1968 and 1971 model years, is a T10 miniature wedge type rated at 12V and 3.78W. Despite sharing the same wedge base style as the 1895, the two are not interchangeable due to their differing physical size and wattage.
• The 1445, 53, and 57 bulbs all share a BA9s bayonet base, yet they are not interchangeable with one another. The 1445 is rated at 2W, the 53 at 2W, and the 57 at 1W, and each corresponds to a specific model year: 1972, 1960, and 1962 respectively.
• The 257 bulb, specified for the 1961 and 1963 model years, is rated at 12V and 2W and is noted as accepting either a festoon or BA9s base configuration, distinguishing it from the other BA9s-base bulbs in this application.
• The BA9s base type is a small bayonet cap with a 9mm cap width, commonly used in instrument panel and indicator lighting. It requires rotational insertion rather than the straight push-fit method associated with wedge-base bulbs.
• Wedge-base bulbs such as the 1895 and 194 are held in place by tension from the socket contacts rather than a locking base, a design that became increasingly common in instrument panel applications during the 1960s and 1970s.
• The wattage variation across these bulbs, ranging from 0.9W for the 1895 to 3.78W for the 194, reflects differences in the intended illumination level and circuit load for the transmission indicator position in each respective model year.