Geo Storm front turn signal bulbs use 1157 size while rear turn signal bulbs use 1156 size. The replacement chart covers 1990 to 1993 model 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 Geo Storm uses the 1157 bulb for the front turn signal across all model years from 1990-1993.
The 1157 is a dual-filament bulb, meaning it serves two lighting functions within a single housing, operating at 21W on the high filament and 5W on the low filament.
The 1157 uses a BAY15d bayonet base, which features two offset pins at different heights to prevent incorrect installation of the bulb.
The rear turn signal on the Geo Storm uses the 1156 bulb for all model years from 1990-1993.
Unlike the 1157, the 1156 is a single-filament bulb rated at 21W, dedicated solely to one lighting function rather than two.
The 1156 uses a BA15s bayonet base, which has two pins at the same height, making it physically incompatible with the BAY15d socket used by the 1157.
Both the 1157 and 1156 operate on a 12V electrical system and conform to ANSI standards recognized in the United States and Canada.
The 1157 and 1156 share the same 15mm base width but differ in pin configuration, so the two bulb types are not interchangeable despite their similar appearance.