The White/GMC WCA front side marker bulb uses a 1157 size, while the rear side marker bulb uses a 194 size. The replacement chart covers vehicle production from 1988 to 1995 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 White/GMC WCA uses the 1157 bulb for the front side marker position across the 1988-1995 model years.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W output, and meets ANSI standards for the US and Canada.
The dual-filament design of the 1157 allows it to serve two separate lighting functions within a single housing, which is a common requirement in combined stop and tail light applications.
The rear side marker position on the White/GMC WCA takes the 194 bulb for the same 1988-1995 span.
The 194 is a miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W, also conforming to ANSI standards for the US and Canada.
The T10 wedge base of the 194 differs fundamentally from the BAY15d bayonet base of the 1157, meaning the two bulb types are not interchangeable between the front and rear side marker positions.
The 1157 and 194 also differ significantly in wattage, with the 1157 drawing considerably more power than the low-wattage 194, which reflects their respective roles in higher-visibility versus low-intensity marker lighting.
Both bulb types are standardized under the ANSI system, which means replacement bulbs carrying the same ANSI designation from different manufacturers share the same electrical and base specifications.