Kenworth C500 front turn signal bulbs use 1157 size while rear turn signal bulbs accommodate either 1156 or 1157 size. The replacement chart covers vehicle production spanning 1981 to 1997 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 Kenworth C500 front turn signal position uses the 1157 bulb across all listed model years from 1981-1997, making it the only bulb type specified for that position.
The 1157 is a dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament, mounted on a BAY15d bayonet base under the ANSI standard recognized in the US and Canada.
The BAY15d base features two offset pins at different heights, a physical design that prevents accidental installation of a single-filament bulb in a socket wired for dual-filament operation.
The rear turn signal position on the Kenworth C500 alternates between the 1157 and the 1156 across different model years, meaning the correct bulb type varies depending on the specific year of the vehicle.
The 1156 is a single-filament bulb rated at 12V and 21W, mounted on a BA15s bayonet base, and shares the same ANSI classification as the 1157.
Although the 1156 and 1157 share a similar physical size and both use a 15mm bayonet base, their base pin configurations differ. The BA15s base has two pins at the same height, while the BAY15d base has offset pins, making the two bulbs mechanically incompatible with each other's sockets.
For the rear turn signal, the 1156 single-filament bulb is specified for the 1981 model year, while the 1157 dual-filament bulb is specified for 1982-1983, reflecting a variation that continues inconsistently through the model range.
Because the rear turn signal specification shifts between the 1156 and 1157 across individual years rather than following a continuous range, year-specific verification is necessary before selecting a replacement bulb for that position.
Both the 1156 and 1157 operate on a 12V electrical system, consistent with standard automotive voltage, and both deliver 21W through their primary or sole filament, producing equivalent light output for turn signal purposes.
The front turn signal socket on the Kenworth C500 is wired to accept the dual-filament 1157, which means substituting a 1156 with its single-filament BA15s base would be physically incompatible with that socket design.