Chevrolet Monza front turn signal bulbs utilize 1034NA and 1157NA sizes, while rear turn signal bulbs use 1156 and 1157 sizes. The replacement chart covers 1975 through 1980 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 front turn signal positions on the Chevrolet Monza use one of two bulb types across the 1975-1980 model years: the 1034NA or the 1157NA, both of which are dual-filament bulbs rated at 12V with a 21W/5W output and fitted with a BAY15d bayonet base.
The 1034NA bulb is a variant of the 1157 and shares its BAY15d base and 12V, 21/5W rating, but is distinguished by its natural amber glass envelope, which produces the amber color without relying on a colored lens.
The 1157NA carries the same natural amber glass characteristic as the 1034NA and is also a dual-filament, BAY15d bayonet base bulb rated at 12V, 21W/5W, making the two types closely related in construction and output.
The rear turn signal positions on the Chevrolet Monza use either the 1156 or the 1157, depending on the model year, and these two bulbs are not interchangeable due to a fundamental difference in filament count and base type.
The 1157 uses a BAY15d bayonet base designed for dual-filament applications, while the 1156 uses a BA15s bayonet base suited for single-filament use. The BAY15d base has offset pins to prevent incorrect installation, whereas the BA15s base has a single contact pin.
The 1156 is rated at 12V and 21W as a single-filament bulb, meaning it operates at one fixed brightness level, unlike the dual-filament 1157, which operates at both 21W and 5W for separate signaling and parking functions.
The front turn signal on the Chevrolet Monza used the 1157NA in 1975 and 1977, while the 1034NA was specified for 1976 and the 1978-1980 model years.
The rear turn signal on the Chevrolet Monza transitioned from the dual-filament 1157, used in 1975-1977, to the single-filament 1156, used in 1978-1980, reflecting a change in rear signal circuit design between those periods.
All four bulb types listed, the 1034NA, 1157NA, 1156, and 1157, conform to ANSI standards recognized in both the United States and Canada, indicating standardized electrical and physical specifications across the range.
Because the 1034NA and 1157NA both use the BAY15d base and share the same wattage ratings as the clear-glass 1157, they are physically compatible with sockets designed for the 1157, but the amber glass on the NA variants serves a distinct optical function that the clear 1157 does not replicate.