Cadillac STS Turn Signal Bulb Size

The Cadillac STS front turn signal requires a 3757NA bulb size for replacement operations. The chart documents bulb specifications across 2005 to 2011 production years.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Front Turn Signal

Years	Bulb Size
2010-2011	3757NA
2005	3757NA

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament wedge bulb (T25), natural amber glass. 12V.	3757NA

Other Locations

Additional Notes

The 3757NA is the front turn signal bulb used across all listed model years of the Cadillac STS, covering 2005 and 2010-2011.
The 3757NA follows the ANSI standard, which is the recognized specification system for automotive bulbs in the United States and Canada.
This bulb is a dual-filament type, meaning it contains two separate filaments within a single housing, allowing it to serve more than one lighting function.
The T25 designation refers to the wedge base style of the bulb, a common base type in automotive applications that seats by friction rather than by a bayonet or screw mechanism.
The natural amber glass of the 3757NA produces an amber-colored output without relying on a colored lens, as the tint is built into the glass envelope itself.
The bulb operates at 12 volts, consistent with the standard electrical system voltage found in passenger vehicles.
The NA suffix in the part number specifically denotes the natural amber glass construction, distinguishing it from clear-glass variants of otherwise similar bulb types.