The Autocar S front turn signal uses a P21W bulb size while the rear turn signal requires a 198 bulb size. The replacement chart covers 1981 to 1983 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 Autocar S uses two distinct bulb standards across its front and rear turn signal positions for the 1981-1983 model years.
The front turn signal on the Autocar S uses the P21W bulb, an ECE-standard type recognized across European and worldwide markets.
The P21W is a single-filament signalling bulb with a BA15s bayonet base, rated at 12V and 21W.
The BA15s bayonet base is a single-contact fitting, meaning it is not interchangeable with dual-contact BA15d variants without modification.
The rear turn signal on the Autocar S uses the 198 bulb, an ANSI-standard type used in the US and Canadian markets.
The 198 is a miniature wedge bulb in the T5 form factor, rated at 12V and 2W, making it significantly lower in wattage than the front P21W.
The wedge base of the 198 bulb relies on wire contacts rather than a bayonet or screw fitting, which means it is physically incompatible with the BA15s socket used by the P21W.
The front P21W and rear 198 bulbs operate on the same 12V supply but differ substantially in wattage, at 21W and 2W respectively, so they are not interchangeable between positions.