Volvo 780 front and rear side marker bulbs use P21/5W and 3893 sizes respectively. The replacement chart covers 1987 to 1991 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Volvo 780 uses two distinct bulb types across its front and rear side marker positions, with each position remaining consistent across the full 1987-1991 model range.
The front side marker on the Volvo 780 calls for the P21/5W bulb, an ECE-standard type used across European and worldwide automotive markets.
The P21/5W is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The BAY15d base features offset pins that prevent incorrect insertion, a design intended to ensure the two filaments are oriented correctly within the housing.
The rear side marker position across all 1987-1991 model years takes the 3893 bulb, an ANSI-standard type used in North American automotive applications.
The 3893 is also a dual-filament, 12V bulb with a BAY15d bayonet base, classified as a specialty application type under the ANSI standard.
Although both the P21/5W and the 3893 share the BAY15d base format, they originate from different standardization systems, ECE and ANSI respectively, and are specified for different positions on the vehicle.
The shared BAY15d base between the two bulb types does not establish interchangeability, as wattage ratings and filament configurations differ between ECE and ANSI classifications.