Cadillac DTS Turn Signal Bulb Size

Additional Notes

• The 4157NA is the sole bulb type listed across all front turn signal positions in these specifications, appearing for the Cadillac DTS from 2006-2011.
• The 4157NA is an ANSI-standardized bulb, meaning it conforms to a defined set of electrical and physical criteria recognized across the United States and Canada.
• The bulb operates on a 12-volt system, which is standard for passenger vehicle electrical architectures of this era.
• As a dual-filament bulb, the 4157NA carries two separate filaments within a single housing, rated at 27 watts and 7 watts respectively, allowing it to serve both a high-intensity and a low-intensity function.
• The T25 designation refers to the bulb's tubular envelope size, with the numeric value indicating the width in eighths of an inch, placing it in a mid-range size category common to automotive signal applications.
• The natural amber glass of the 4157NA produces its amber output through the color of the glass itself rather than through a coated or painted lens, which distinguishes it from clear-glass variants such as the 4157 used behind amber-tinted housings.
• The "NA" suffix in the part number specifically denotes the natural amber glass construction, and substituting a non-NA variant would alter the color output at the lens.
• The consistent 4157NA fitment across all six model years indicates no mid-cycle revision to the front turn signal housing or socket type occurred on the Cadillac DTS during the 2006-2011 production span.