Cadillac Series 61 front and rear turn signal bulbs both utilize a 1154 size bulb. The replacement chart covers 1950 to 1951 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Cadillac Series 61 uses the 1154 bulb for both front and rear turn signals across the 1950-1951 model years.
The 1154 is an ANSI-standardized bulb type recognized in both the United States and Canada.
It is a dual-filament bulb, meaning it contains two separate filaments within a single envelope, allowing it to serve more than one lighting function.
The 1154 uses a BAY15d bayonet base, a two-pin offset base design that physically locks the bulb into its socket with a twist.
The 1154 is noted as an older variant of the 1157, indicating the two types share a related design lineage but are not the same part.
The 1154 is rated for both 6V and 12V electrical systems, reflecting the transitional voltage standards common in vehicles of that era.
Because the 1154 and 1157 are related but distinct variants, substitution between the two warrants caution, as socket and electrical compatibility cannot be assumed without verification.
The uniform use of the 1154 across all four turn signal positions on the Series 61 means a single bulb type covers the complete turn signal fitment for both model years listed.