The Mercedes-Benz GL450 front inner turn signal requires a 3457NA or 3357NA bulb size, while the front turn signal uses a PY24WNA or 3457NA bulb size, and the rear turn signal requires a 12496 or PY21W bulb size. The replacement chart covers vehicle production years spanning 2007 to 2016 with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 3457NA is the most frequently specified bulb across the Mercedes-Benz GL450 turn signal positions, appearing in the front inner turn signal for 2007-2012, the front turn signal for 2011-2012, and the front turn signal (side rearview mirror) for 2007-2010. It is a dual-filament T25 wedge bulb rated at 12V with a 27W main filament and a 7W secondary filament, finished in natural amber glass under the ANSI standard applicable to the US and Canada.
The 3357NA differs from the 3457NA in that it carries only a single filament rated at 27W, making the two bulbs functionally non-interchangeable despite sharing the same T25 wedge form and natural amber glass construction. The GL450 front inner turn signal for 2010 is the sole position in these specifications calling for the 3357NA.
The PY24WNA is specified for the front turn signal of the GL450 for 2013-2016, exclusively on vehicles equipped with halogen capsule headlamps. It uses a PGU20-4 base and is rated at 12V, 24W. It is the ANSI-market amber variant of the ECE-standard PY24W, and the two are not interchangeable due to base and regulatory differences.
The PY21W is an ECE-standard bulb with a BAU15s bayonet base, rated at 12V and 21W. Its presence in the GL450 rear turn signal for certain model years reflects the international regulatory origin of the vehicle platform, as the ECE standard governs lighting equipment across Europe and many other markets outside North America.
The BAU15s base of the PY21W is an offset single-contact bayonet fitting. The offset pin arrangement is a deliberate design feature that prevents substitution with non-amber bulbs sharing a standard BA15s base, which is a fitment safeguard relevant to turn signal applications where amber color output is legally required.
The 12496 is a Philips/Osram part number designation rather than an ANSI or ECE standard code, indicating a proprietary or specialty halogen bulb rated at 12V. It is specified for the GL450 rear turn signal in 2007, 2010, and 2012, alternating with the PY21W across adjacent model years in that position.
The rear turn signal of the GL450 does not use a consistent bulb type across its model year range. The 2007, 2010, and 2012 model years call for the 12496, while 2008, 2009, and 2011 call for the PY21W. These two bulbs differ in base type, standard classification, and wattage, and are not interchangeable.
For the GL450 front turn signal in 2007-2010, the specified 3457NA is noted as a side rearview mirror application, distinguishing it from a conventional front fascia turn signal position. This placement detail is relevant to part sourcing and socket compatibility.
The NA suffix on the 3457NA, 3357NA, and PY24WNA designations indicates natural amber glass, meaning the amber color is produced by the glass envelope itself rather than by an amber-coated clear bulb. This distinction affects optical output and regulatory compliance in markets that specify true amber rather than coated equivalents.
The PGU20-4 base of the PY24WNA is a wedge-type fitting specific to that bulb family and is not compatible with the T25 wedge base used by the 3457NA or 3357NA, nor with the BAU15s bayonet base of the PY21W. Each of the four base types present in these specifications requires a distinct socket.