The Volvo S40 side marker utilizes a 12961 bulb size for illumination purposes across various production periods. Data for the specific component covers a span from 2000 through 2011.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Volvo S40 front side marker position uses the 12961 bulb across the 2005-2011 model years.
The 12961 is a Philips part number designating a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W.
The T10 wedge base format is a push-in fitment with no locking rotation required, which distinguishes it from bayonet-style bases.
The Volvo S40 rear side marker position carries two bulb types simultaneously: the P21/5W for 2005-2011 and the 12961 for 2000-2011.
The P21/5W follows the ECE international standard and uses a BAY15d offset-pin bayonet base, which is not interchangeable with the W2.1x9.5d wedge base of the 12961.
The P21/5W is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, whereas the 12961 is a single-filament 5W bulb.
Because the BAY15d bayonet base and the W2.1x9.5d wedge base are physically distinct, the P21/5W and the 12961 are not interchangeable despite both appearing in the rear side marker position of the S40.
The offset-pin design of the BAY15d base is a deliberate anti-reversal feature, ensuring the dual-filament P21/5W bulb is seated in only one orientation within its socket.
The 12961 designation in the rear side marker data extends back to the 2000 model year, covering a longer fitment range than the P21/5W entries in that same position.
When servicing the rear side marker on the Volvo S40, the socket type present in the housing determines which of the two listed bulbs is the correct fitment, as the base formats are mechanically incompatible with each other.