The Mercedes-Benz E420 front turn signal requires a 1156NA bulb size, while the rear turn signal uses a 1156NA with PY21W designation. The replacement chart covers 1994 to 1997 model years with corresponding bulb size specifications for each signal location.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz E420 uses three distinct bulb types across its turn signal positions and model years: the 1156NA, P21/5W, and PY21W.
The 1156NA is an ANSI-standard bulb used in North American markets. It is a single-filament type with a BA15s bayonet base, natural amber glass, and a 12V, 21W rating. The E420 uses this bulb for both front and rear turn signals in the 1997 model year.
The P21/5W follows the ECE standard used in European and worldwide markets. Unlike the other bulbs in these specifications, it carries a dual-filament design rated at 12V, 21W/5W, and mounts on a BAY15d bayonet base. It appears on the E420 front turn signal position for the 1994-1995 model years.
The PY21W is also an ECE-standard bulb, single-filament with an amber-tinted glass envelope, rated at 12V, 21W. Its base is a BAU15s bayonet type. It is specified for the E420 rear turn signal in the 1994-1995 model years.
The base types across these three bulbs are not interchangeable. The BA15s, BAY15d, and BAU15s bayonet bases differ in pin offset and spacing, meaning a bulb with one base type cannot be seated into a socket designed for another.
The 1997 E420 uses the same bulb, the 1156NA, for both front and rear turn signal positions, while the 1994-1995 model years use different bulbs for each position, the P21/5W at the front and the PY21W at the rear.
Although the P21/5W and PY21W share the same single-filament wattage of 21W, the P21/5W carries a second 5W filament, making it a dual-filament bulb. This additional filament serves a secondary lighting function and is tied to the BAY15d base, which has two pins at equal offset to support both circuits.
The natural amber glass of the 1156NA achieves its amber output through the glass coating rather than a clear envelope, distinguishing it from the standard 1156, which produces white light. The PY21W similarly produces amber light through its glass, while the P21/5W produces white light from a clear envelope.
The shift from ECE-standard bulbs in 1994-1995 to the ANSI-standard 1156NA in 1997 reflects a change in the regional specification applied to the E420 across those model years.