The Chevrolet S7 front side marker uses a 1157 bulb size, while the rear side marker accommodates either 194 or 1157 bulb sizes. The replacement chart covers 1987 to 1988 vehicle 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 Chevrolet S7 side marker system across 1987-1988 relies on two distinct bulb types: the 1157 and the 194, both conforming to ANSI standards recognized in the United States and Canada.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V and drawing 21W on its primary filament and 5W on its secondary filament. The two filaments serve different lighting functions within the same housing.
The BAY15d bayonet base on the 1157 features offset pins, a design that prevents incorrect insertion by ensuring the bulb can only be seated in one orientation.
The 194 is a single-filament miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W. Its wedge base relies on direct contact with the socket rather than a locking pin mechanism.
Because the 1157 uses a bayonet base and the 194 uses a wedge base, the two bulb types are not interchangeable with each other, regardless of voltage compatibility.
For the Chevrolet S7, the front side marker position uses the 1157 bulb for both 1987 and 1988.
The rear side marker position differs between model years. The 1987 S7 uses the 1157, while the 1988 S7 uses the 194 in that same position.
The shift from a 21W/5W dual-filament 1157 to a 3.78W single-filament 194 in the 1988 rear side marker represents a significant reduction in wattage, which affects socket and wiring compatibility when replacing bulbs across these two years.