The White/GMC WAH front side marker bulb uses a 1157 size, while the rear side marker bulb uses a 194 size. The replacement chart covers 1990 to 1995 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 White/GMC WAH uses the 1157 bulb for the front side marker position across the 1990-1995 model years.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with filaments drawing 21W and 5W respectively.
The BAY15d bayonet base features offset pins, which physically prevents substitution with single-filament bayonet bulbs that share a similar base profile.
The rear side marker position on the WAH uses the 194 bulb across the same 1990-1995 model years.
The 194 is a single-filament miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W.
Both the 1157 and 194 conform to ANSI standards applicable in the United States and Canada.
The front and rear side marker positions on the WAH require different bulb types, and the two are not interchangeable due to differences in base type, wattage, and filament count.
The low wattage of the 194 at 3.78W reflects its role as a low-intensity marker lamp, whereas the 1157 supports higher output through its 21W filament for more prominent front marker visibility.