Cadillac ATS Turn Signal Bulb Size

Additional Notes

• The front turn signal positions across the Cadillac ATS model years covered in these specifications use one of two bulb sizes: the 7444NA or the 7443NA. Both belong to the T20 wedge family and share the same voltage and wattage ratings of 12V with a dual-filament output of 21W and 5W.
• The 7444NA and 7443NA are both classified under the ANSI standard applicable to the United States and Canada. This classification indicates the bulbs conform to a standardized set of electrical and physical requirements recognized across North American vehicle markets.
• Both bulb types feature a natural amber glass envelope, which filters the light output to produce an amber color without relying on a colored lens or a coated filament housing. This construction method is the defining characteristic of the "NA" suffix in both part numbers.
• The dual-filament design of both bulbs means a single unit serves two separate lighting functions within the same socket. In a front turn signal application, the lower 5W filament typically handles a parking or daytime running light function, while the higher 21W filament handles the active turn signal flash.
• The 2017 and 2015-2016 model years show a split in fitment, with 2017 and 2015 using the 7443NA while 2016 uses the 7444NA. This indicates the two part numbers are not interchangeable across all ATS model years despite their shared T20 form factor and identical voltage and wattage ratings.
• The 2018-2019 model years both specify the 7444NA, and the 2013-2015 model years specify the 7443NA, with the exception of 2016 which returns to the 7444NA. The alternating fitment pattern across the production run reflects that the 7443NA and 7444NA, while visually and electrically similar, carry distinct ANSI designations that correspond to specific socket or base configurations.
• The T20 wedge base is a common automotive bulb format used widely in turn signal and tail light applications. The wedge base design means the bulb is held in place by the socket walls rather than by a bayonet or screw mechanism, which affects how the bulb is seated and removed during replacement.
• The 12V operating voltage of both bulb types is standard for modern passenger vehicle electrical systems, which operate on a nominal 12-volt DC supply. This voltage rating is consistent with the Cadillac ATS platform's electrical architecture.