Cadillac DeVille Back Up Light Bulb Size

Additional Notes

• The 1156 bulb is the most frequently specified size across the Cadillac DeVille's back up light history, covering model years 1961-1989 with the exception of 1988-1989, and spanning the full range from 1961 through 1988, making it the dominant fitment across the broadest span of production years.
• The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W. Its single-filament design means it serves one lighting function only, which is consistent with its use in a dedicated back up light application.
• The 1073 bulb shares the same BA15s bayonet base as the 1156 but operates at a lower wattage of 13W versus 21W. The Cadillac DeVille used the 1073 in 1953-1958 and again in 1960, meaning the two physically similar bulbs are not interchangeable due to their differing wattage output.
• The 1959 DeVille uses the 1156 rather than the 1073 that surrounds it in adjacent model years, representing a single-year fitment difference within an otherwise 1073-dominant era for that period.
• The 3057 and 3157 are both dual-filament T25 wedge bulbs rated at 12V with identical wattage values of 27W and 7W. Despite their near-identical electrical specifications, they are distinct part numbers and are not guaranteed to be interchangeable without confirming socket compatibility.
• The 2057 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V, 26.9W and 8W. It is described as a brighter variant of the 1157, and the Cadillac DeVille used it for back up lights in model years 1994-1999.
• The shift from the 2057 to the 3157 occurred between the 1999 and 2000 DeVille. Both are dual-filament bulbs, but they use different base types, the 2057 using a BAY15d bayonet base and the 3157 using a wedge base, making them physically incompatible with each other's sockets.
• The 3057 was used in the 1989-1993 DeVille back up lights. It preceded the 2057 in the fitment sequence, and while both are dual-filament bulbs, their differing base types mean one cannot substitute for the other.
• All five bulb types specified across the DeVille's production history conform to ANSI standards applicable in the United States and Canada, indicating standardized electrical and physical tolerances across all listed model years.
• The back up light bulb specification for the Cadillac DeVille transitioned through four distinct bulb types in chronological order: 1073 and 1156 in the earlier decades, followed by 3057, then 2057, and finally 3157 in the most recent years covered.