The Autocar AT front turn signal bulb uses a 1156 size, while rear turn signal bulbs use 1157 and 198 sizes. The replacement chart covers vehicle production years from 1983 to 1988 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 Autocar AT uses the 1156 bulb for the front turn signal across all listed model years, 1983-1988.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W under the ANSI standard applicable in the US and Canada.
A single filament means the 1156 serves one lighting function only, which is consistent with its dedicated turn signal role at the front.
The rear turn signal specification shifts between two different bulb types depending on the model year of the Autocar AT.
For the 1985-1988 rear turn signal, the specified bulb is the 1157, a dual-filament type with a BAY15d bayonet base, rated at 12V with filaments drawing 21W and 5W respectively.
The dual-filament design of the 1157 allows it to serve two distinct brightness levels within a single housing, commonly used where a turn signal and a running or brake light share the same lamp position.
The 1983-1984 rear turn signal uses the 198 bulb instead, a miniature wedge type in the T5 form factor, rated at 12V and 2W.
At 2W, the 198 bulb operates at a significantly lower wattage than either the 1156 or the 1157, reflecting its classification as a miniature indicator-grade lamp.
The 1157 and the 198 are not interchangeable. The 1157 uses a BAY15d bayonet base while the 198 uses a wedge base, and their wattage ratings differ substantially.
All three bulb types, the 1156, 1157, and 198, conform to ANSI standards recognized in the US and Canada.