The Mercedes-Benz GLA250 front turn signal uses bulb sizes 3457NA and 12496, while the rear turn signal requires 12496 and PY21W bulb sizes. The replacement chart covers 2015 to 2020 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 Mercedes-Benz GLA250 turn signal bulb specifications apply exclusively to trims equipped with Halogen Capsule Headlamps, as this condition is noted across all listed model years for both front and rear positions.
The 3457NA is the most frequently specified front turn signal bulb in these records, appearing in the 2015-2018, 2020 GLA250 front position. It is a dual-filament T25 wedge bulb rated at 12V with a 27W main filament and a 7W secondary filament, produced to ANSI standards for the US and Canadian markets.
The natural amber glass construction of the 3457NA produces its amber signal color directly from the bulb envelope rather than relying on a colored lens, which is a characteristic of the NA designation in the ANSI naming system.
The 12496 is a Philips/Osram part number designating a 12V halogen bulb for specialty automotive applications. It serves as the rear turn signal bulb for the 2015, 2017-2020 GLA250 and also appears as the front turn signal bulb for the 2019 model year.
The PY21W is specified for the rear turn signal position on the 2016 GLA250. It is a single-filament amber bulb rated at 12V and 21W, conforming to ECE standards used in European and international markets, and it uses a BAU15s offset bayonet base.
The BAU15s base of the PY21W is not interchangeable with the standard BA15s base found on many other automotive bulbs. The offset pin arrangement is a deliberate design feature intended to prevent incorrect bulb installation.
The 3457NA and PY21W are not interchangeable despite both being amber single-signal bulbs. They differ in base type, wattage, filament count, and regulatory standard, making substitution between them incompatible without modification.
The front turn signal position on the 2019 GLA250 uses the 12496, while all surrounding model years in the same position use the 3457NA, indicating a year-specific fitment distinction for that position.
The rear turn signal position on the 2016 GLA250 uses the PY21W, while all other listed model years in that position use the 12496, making 2016 the sole year in these records with a PY21W rear fitment.
Because the 12496 is identified by a manufacturer part number rather than an ANSI or ECE standard designation, cross-referencing to equivalent bulbs from other manufacturers requires verification against Philips and Osram compatibility data rather than a universal standard.