Mercedes-Benz E43 AMG Turn Signal Bulb Size

Mercedes-Benz E43 AMG front turn signal requires a PY21W bulb size. The replacement chart covers 2017 to 2018 model years with corresponding bulb specifications.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Front Turn Signal

Years	Bulb Size
2017-2018	PY21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament amber bulb with BAU15s bayonet base. 12V, 21W.	PY21W

Other Locations

Additional Notes

The PY21W is the specified bulb type for the front turn signal on the Mercedes-Benz E43 AMG across the 2017-2018 model years.
The PY21W operates at 12 volts and 21 watts, placing it in the standard single-filament category typical of dedicated turn signal applications.
The PY21W produces amber light natively through its glass envelope rather than through a clear bulb with an amber lens, which is a defining characteristic of this bulb type under ECE regulations.
The BAU15s bayonet base on the PY21W features offset pins, distinguishing it physically from the BA15s base used on clear single-filament bulbs such as the P21W. This offset prevents installation of an incorrect bulb type into the socket.
The PY21W conforms to ECE standards, which govern lighting regulations across Europe and many markets worldwide, making it a globally recognized specification rather than a region-specific one.
Because the BAU15s base is keyed differently from other 15mm bayonet bases, substitution with visually similar bulbs of a different base type is not mechanically possible without modification to the socket.