The BMW L7 front turn signal requires a P21/5W bulb size while the rear turn signal uses a P21W bulb size. The replacement chart covers 1986 to 1987 model production 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.
The BMW L7 uses two distinct ECE-standard bulb types across its front and rear turn signal positions for the 1986-1987 model years.
The front turn signal on the BMW L7 takes a P21/5W bulb, which is a dual-filament type rated at 12V with a 21W main filament and a 5W secondary filament.
The P21/5W uses a BAY15d bayonet base, an offset twin-pin fitting that prevents incorrect insertion by physically distinguishing the two filament circuits.
The rear turn signal uses a P21W bulb, a single-filament type rated at 12V and 21W, mounted on a BA15s bayonet base with a single center pin.
The BA15s base of the P21W and the BAY15d base of the P21/5W are not interchangeable, as the pin configurations differ between the two base types.
Both bulb types conform to ECE regulations, indicating suitability for European and worldwide markets rather than North American DOT standards.
The 21W output rating is shared by both bulb types, meaning both the front and rear turn signal positions operate at the same primary wattage.
The dual-filament design of the P21/5W in the front position allows a single bulb to serve more than one lighting function, with the 5W filament typically assigned to a secondary role such as a parking or position light.