Volvo V40 front fog light bulbs use H3 size while rear fog light bulbs use P21W size. The replacement chart covers 2000 to 2004 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 V40 uses the H3 bulb for its front fog lights across the 2000-2004 model years.
The H3 is a single-filament halogen bulb operating at 12V and 55W, fitted with a PK22s base, and manufactured to ECE standards with approval also granted in the United States and Japan.
The PK22s base on the H3 is a pinch-base design, which differs from the bayonet and wedge bases found on other automotive bulb types, making it non-interchangeable with those formats.
The rear fog lights on the Volvo V40 use the P21W bulb across the same 2000-2004 model years.
The P21W is a single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base, and also produced to ECE standards.
The BA15s base on the P21W is a single-contact bayonet fitting. It is not interchangeable with the BA15d base, which carries two contacts and is used in dual-filament applications.
Both the H3 and P21W operate on a 12V electrical system, consistent with the standard automotive voltage found in the Volvo V40.
The H3 at 55W draws significantly more power than the P21W at 21W, reflecting the functional difference between an illumination bulb used for forward visibility and a lower-intensity signalling bulb used for rear fog warning.