Freightliner FL70 front turn signal bulbs use 1156 size while rear turn signal bulbs use 1157 size. The replacement chart covers 1991 to 2005 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 Freightliner FL70 uses the 1156 bulb for the front turn signal across all listed model years, 1991-2005, without variation.
The 1156 is a single-filament bulb operating at 12 volts and 21 watts, fitted with a BA15s bayonet base, and classified under the ANSI standard applicable in the United States and Canada.
The rear turn signal on the FL70 calls for the 1157 bulb across the same 1991-2005 model year span.
The 1157 is a dual-filament bulb rated at 12 volts with a 21W/5W filament configuration, mounted on a BAY15d bayonet base, also governed by the same ANSI standard.
The BA15s base of the 1156 and the BAY15d base of the 1157 are physically distinct and not interchangeable. The BAY15d base features offset pins to prevent incorrect installation, while the BA15s base has symmetrical pins.
The dual-filament design of the 1157 serves two separate circuit functions, with the higher-wattage filament dedicated to the turn signal and the lower-wattage filament typically serving a running light function.
Because the 1156 carries only a single filament, it is not a direct substitute for the 1157 in rear positions where a dual-filament function is required by the socket wiring.
Both bulb types share the same 12-volt operating voltage, which reflects the standard electrical system voltage common to commercial vehicles of this class.