The Volvo 240 brake light uses a P21/5W bulb size for the rear lighting system. Data for the specific component covers the period from 1990 through 1993.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Volvo 240 uses two distinct bulb types across its brake lighting system for the 1990-1993 model years: the P21/5W for the primary brake lights and the P21W for the center high mount stop light.
Both the P21/5W and P21W are ECE-standard bulbs, a specification framework used in Europe and internationally, meaning they conform to internationally recognized performance and safety standards rather than SAE standards common in North American applications.
The P21/5W is a dual-filament bulb, which allows it to serve two functions within a single housing. In the context of the Volvo 240 brake lights, this dual-filament design typically supports both the running light and the brake light functions from one bulb position.
The P21/5W operates at 12 volts with a 21W filament for the brighter function and a 5W filament for the secondary function, and it uses a BAY15d bayonet base. The offset pins of the BAY15d base are a deliberate design feature that prevents incorrect installation of the two filaments.
The P21W used in the Volvo 240 center high mount stop light is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base. Because it serves only one function, a single filament is sufficient for this application.
The BAY15d base of the P21/5W and the BA15s base of the P21W are physically distinct and not interchangeable. Attempting to fit a P21W into a P21/5W socket, or vice versa, is not possible without modification due to the differing base configurations.
The P21/5W and P21W share the same 21W primary filament output and the same general bayonet-style mounting family, which can create confusion when sourcing replacements. The critical distinction lies in the base type and the presence or absence of a secondary filament.