Mercedes-Benz G550 Turn Signal Bulb Size

Additional Notes

• The three bulb types specified across the Mercedes-Benz G550 turn signal positions are the 12496, PY21W, and 1156NA, all rated at 12 volts.
• The PY21W is the most frequently specified bulb across both front and rear turn signal positions on the G550, appearing in the majority of model years covered.
• The PY21W follows the ECE standard and uses a BAU15s bayonet base, a single-filament construction, and an amber output at 21 watts. Its offset pin arrangement in the BAU15s base distinguishes it physically from visually similar bayonet bulbs.
• The 1156NA is an ANSI-standard bulb with a BA15s bayonet base and natural amber glass to produce its amber output, also rated at 21 watts. Its BA15s base uses symmetrical pins, making it physically incompatible with the BAU15s socket used by the PY21W despite the two bulbs sharing the same wattage and voltage rating.
• The front turn signal on the Mercedes-Benz G550 used the 1156NA exclusively in 2009-2010, after which the specification shifted to other bulb types in subsequent years.
• The 12496 is a Philips/Osram part number designating a halogen bulb for specialty applications at 12 volts. It does not correspond to a broad ANSI or ECE category, meaning fitment is tied more closely to the specific part number than to a general standard.
• The front and rear turn signal positions on the G550 do not consistently share the same bulb type within a given model year. For example, in 2015 the front position uses the 12496 while the rear uses the PY21W, and in 2014 the front uses the PY21W while the rear uses the 12496.
• Because the BA15s and BAU15s bases are not interchangeable, substituting a 1156NA for a PY21W, or vice versa, is not possible without a socket adapter, even though both bulbs operate at 12 volts and 21 watts.
• The 12496 designation as a manufacturer-specific part number means cross-referencing to ANSI or ECE equivalents requires verification against manufacturer compatibility data rather than relying on standardized category matching.
• In 2012, the front turn signal on the G550 uses the 12496 while the rear uses the PY21W, a split that also occurs in reverse during 2014, when the front uses the PY21W and the rear uses the 12496.