The BMW 323i brake uses bulb size P21W and bulb size P21/5W according to the provided specifications. Data for the specified components covers the range from 1998 to 2000.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW 323i uses three distinct ECE-standard bulb types across its brake lighting system: P21W, P21/5W, and P21/4W.
The P21W is a single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base. It is used in the outer brake positions across all three model years covered.
The P21/4W is a dual-filament signalling bulb rated at 12V with filaments at 21W and 4W. It uses a BAZ15d bayonet base and serves the inner brake position on the 323i for 1998-2000.
The P21/5W is a dual-filament signalling bulb rated at 12V with filaments at 21W and 5W. Its BAY15d bayonet base physically differs from both the BA15s of the P21W and the BAZ15d of the P21/4W.
The three bayonet base types, BA15s, BAY15d, and BAZ15d, are not interchangeable. Each base has a distinct pin configuration that prevents incorrect installation across socket types.
The BMW 323i (1998) uses a P21/5W for its brake bulb position, while the 1999-2000 model years use a P21W in that same position. These two bulbs carry different base types and filament configurations.
The inner brake position on the 323i remains consistent at P21/4W across 1998-2000, while the general brake and outer brake positions each follow their own fitment patterns across those years.
All bulb types specified for the 323i conform to ECE regulations, a standard recognized across Europe and numerous other markets worldwide.