Cadillac Series 62 Back Up Light Bulb Size

The Cadillac Series 62 back up light utilizes P21W and 1073 bulb sizes for the rear illumination system. Data for the specific lighting components covers the range from 1953 to 1964.

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
1958-1964	P21W
1953-1957	1073

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	1073

Other Locations

Additional Notes

The Cadillac Series 62 back up light specifications cover model years 1953 through 1964, spanning two distinct bulb types across that period.
Both the P21W and the 1073 use a BA15s single-contact bayonet base, meaning the physical mounting interface is identical between the two bulb types.
Despite sharing the same BA15s base, the P21W and the 1073 are not electrically equivalent. The P21W operates at 21W while the 1073 operates at 13W, a difference that makes direct substitution inadvisable without accounting for the wattage variance.
The 1964-1958 Cadillac Series 62 specifies the P21W, an ECE-standard bulb common in European and worldwide automotive applications.
The P21W is a single-filament bulb rated at 12V and 21W, designed for signalling functions such as back up lighting.
The 1957-1953 Cadillac Series 62 specifies the 1073, an ANSI-standard bulb used in North American automotive applications.
The 1073 is a single-filament bulb rated at 12V and 13W, and it is a lower wattage variant of the more widely known 1156 bulb, which shares the same BA15s base but draws higher wattage.
The shift from the 1073 to the P21W between the 1957 and 1958 model years represents a change in both the applicable bulb standard and the operating wattage of the back up light circuit.