The Porsche 928 front and rear side marker bulb sizes include 12821, 5008, and 232 specifications for this model. The replacement chart covers 1978 to 1995 production years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Porsche 928 front and rear side marker positions draw from three distinct bulb types across the model's production span: the 12821, 5008, and 232.
The 5008 is the most frequently specified bulb across both positions on the Porsche 928, appearing in the front side marker from 1981-1989 and 1991-1994, and in the rear side marker across numerous model years within the same general range.
The 5008 is an ANSI-standard single-filament bulb rated at 12V with a BA15s bayonet base. It is a lower-wattage variant of the 1156 bulb, meaning the two share a base type but are not wattage-equivalent and are not interchangeable without consequence.
The 12821 is a Philips part number designating a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W. Its wedge-style base differs fundamentally from the bayonet and festoon bases used by the other two bulb types in these specifications.
On the Porsche 928, the 12821 appears in the front side marker for the 1978-1980 model years and again in 1995, and in the rear side marker for 1978-1980. The base type of the 12821 is physically incompatible with sockets designed for the BA15s or SV8.5 bases used by the 5008 and 232.
The 232 is an ANSI-standard festoon bulb with an SV8.5 base, rated at 12V and 3W. Festoon bulbs seat by compression between two end caps rather than by insertion into a socket, making them physically distinct from both wedge and bayonet-base bulbs.
The 232 festoon bulb is specified for the front side marker only in 1990 and 1995 on the 928, while in the rear position it is listed for 1982, 1986, and 1993-1994. Its presence in isolated years, surrounded by years calling for the 5008, reflects housing or socket changes rather than a uniform fitment across the model's run.
The 1990 model year presents a notable split: the front side marker calls for the 232 festoon bulb while the rear calls for the 5008 bayonet-base bulb, confirming that front and rear sockets are not shared and the two positions require separate bulb selections.
The 1991 model year shows the reverse arrangement from 1990, with the front side marker returning to the 5008 and the rear side marker also using the 5008, making it one of the years where both positions share the same bulb type.
Because the 12821, 5008, and 232 each use a different base type, none of the three bulbs specified across these positions is a drop-in substitute for either of the other two, regardless of voltage compatibility.