The Saab 900 front fog light uses an H3 bulb size while the rear fog light requires a P21W bulb size. Replacement specifications for the Saab 900 fog light bulbs span a chart covering 1987 to 1998 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Saab 900 front fog light uses the H3 bulb across all listed model years from 1987 to 1998.
The H3 is a single-filament halogen bulb operating at 12V and 55W, fitted with a PK22s base, and certified under ECE standards for use in Europe and worldwide, with additional approval in the United States and Japan.
The PK22s base on the H3 is a pinch-type connector, which differs from the bayonet and wedge bases found on other common automotive bulb types, making it non-interchangeable with those formats.
The Saab 900 rear fog light uses the P21W bulb for model years 1995-1998.
The P21W is a single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base, and also certified under ECE standards.
The BA15s base on the P21W is a single-contact bayonet fitting, which is mechanically and electrically distinct from the PK22s base used on the H3, meaning the two bulb types are not interchangeable with each other.
The wattage difference between the H3 (55W) and the P21W (21W) reflects their respective roles, with the higher-output H3 serving the forward-facing fog light function and the lower-output P21W serving the rear signalling function.