Alfa Romeo 164 front turn signal bulbs use 1156 size while rear turn signal bulbs use P21W size. The replacement chart covers 1991 to 1995 vehicle 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 Alfa Romeo 164 uses the 1156 bulb for the front turn signal across all model years from 1991-1995.
The rear turn signal on the Alfa Romeo 164 uses the P21W bulb across the same 1991-1995 model year span.
The 1156 is an ANSI-standard bulb, meaning it conforms to North American specifications used in the United States and Canada.
The P21W is an ECE-standard bulb, governed by the Economic Commission for Europe regulations and used in European and worldwide markets.
Both the 1156 and P21W operate at 12 volts with a 21-watt output and are single-filament bulbs, meaning each serves only one lighting function rather than combining two.
Both bulbs share the BA15s bayonet base, a single-contact bayonet fitting with a 15mm base width, which accounts for their physical interchangeability at the socket level.
Despite sharing the same base type and electrical ratings, the 1156 and P21W are governed by different regional standards, and substituting one for the other may affect regulatory compliance depending on the market in which the vehicle is operated.