BMW 325i front inner and outer turn signal assemblies utilize bulb sizes PY21W, P21W, and 12961, while rear turn signal applications require the P21W bulb size. The replacement chart documents bulb specifications across 1988 to 2006 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W is the most widely used bulb type across the BMW 325i turn signal specifications, appearing in the front inner, rear, and front positions across model years 2001-2006 for the modern generation and 1988-1995 for the earlier generation. It is a single-filament ECE-standard signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The PY21W shares the same 12V, 21W rating as the P21W but differs in two important ways: its BAU15s base is offset rather than straight, and the bulb itself is amber-tinted. These physical differences make the PY21W and P21W non-interchangeable despite their near-identical power ratings.
The 2006 BMW 325i front inner turn signal position specifies the PY21W exclusively, whereas the same position on 2001-2005 models specifies the P21W. This represents a base-type change between those model years that affects direct substitution.
For model years 2002-2005, the front turn signal position lists both a P21W (white) and a PY21W (yellow) option, indicating that the correct fitment depends on the lens or housing color of the specific vehicle configuration.
The 12961 is a Philips-designated miniature wedge bulb of the T10 type, using a W2.1x9.5d base and rated at 12V, 5W. Its significantly lower wattage distinguishes it from the P21W and PY21W used in primary signal positions.
The 12961 bulb appears consistently across all six model years from 2001-2006 in the front outer turn signal position, as well as in the side sub-position of the front turn signal for those same years.
The P21/5W, used in the front turn signal position on the 1988-1995 BMW 325i, is a dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament. Its BAY15d bayonet base has two pins at different heights, preventing installation in sockets designed for single-filament BA15s or BAU15s bases.
The rear turn signal position uses the P21W uniformly across all listed years from 1988-2006, with no variation in bulb type between the earlier and later vehicle generations.
The three bayonet base types present in these specifications, BA15s, BAU15s, and BAY15d, are physically distinct. The offset pin of the BAU15s and the staggered dual pins of the BAY15d each prevent cross-installation with the other base types, making base identification a necessary step before substitution.
The front turn signal position on the 1988-1995 BMW 325i uses the P21/5W, while the rear turn signal on those same years uses the P21W. Although both are ECE-standard bayonet bulbs at 12V and 21W, their differing base types and filament configurations mean they are not interchangeable with each other.