Chevrolet Spectrum front turn signal bulbs use 1157 size while rear turn signal bulbs use 1073 or 1156 size. The replacement chart covers 1985 to 1988 vehicle production 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 Chevrolet Spectrum uses the 1157 bulb for the front turn signal across all four model years covered, 1985-1988.
The 1157 is a dual-filament bulb operating at 12V with a 21W/5W output and a BAY15d bayonet base, conforming to ANSI standards for the US and Canadian markets.
Its dual-filament design allows a single housing to serve two functions, typically combining turn signal and parking light duties at different wattage levels.
The rear turn signal specification for the Chevrolet Spectrum changed between model years, with the 1988 model year using a different bulb than the 1985-1987 model years.
The 1985-1987 Spectrum rear turn signal uses the 1156, a single-filament bulb with a BA15s bayonet base rated at 12V and 21W, also conforming to ANSI standards.
The 1988 Spectrum rear turn signal uses the 1073, a single-filament bulb sharing the same BA15s bayonet base as the 1156 but rated at a lower 13W output.
Because the 1073 and 1156 share the BA15s base, they are physically interchangeable in terms of socket fitment, though their wattage ratings differ and substitution may affect circuit behavior.
The BAY15d base of the 1157 is not the same as the BA15s base used by the 1073 and 1156, making front and rear bulbs physically incompatible with each other's sockets.