The Chevrolet S7 front and rear turn signal bulbs both utilize a 1157 size bulb for proper operation. The replacement chart covers vehicle production spanning 1987 to 1988.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1157 is the sole bulb type across all listed positions and years for the Chevrolet S7, covering both front and rear turn signal applications for 1987-1988.
The 1157 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical standards shared across those markets.
It is a dual-filament bulb, which means it contains two separate tungsten filaments within a single envelope, each operating independently at different wattages.
The two filaments operate at 21W and 5W respectively, with the higher-wattage filament typically serving the active turn signal function and the lower-wattage filament serving a secondary role such as a parking or running light.
The 1157 uses a BAY15d bayonet base, a two-pin base type where the two pins are offset at different heights, a physical design that prevents incorrect single-filament bulbs from being seated in the socket.
The bulb operates on a 12V electrical system, consistent with the standard automotive voltage found in conventional passenger vehicles and light trucks of that era.
Because the BAY15d base is offset by design, a single-filament bulb with a BAY15s base, where both pins sit at the same height, is not interchangeable with the 1157 even if the outer envelope size is similar.
The 1157 shares its BAY15d base type with several other bulb numbers, such as the 2057 and 3496, though those variants differ in wattage ratings and are not direct replacements without verifying electrical compatibility.