The White/GMC WIA uses 1157 bulb size for both front and rear turn signal applications. Replacement chart data spans 1988 to 1995 model 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 WIA uses the 1157 bulb for both its front and rear turn signals across the 1988-1995 model years.
The 1157 is a dual-filament bulb, meaning it carries two separate filaments within a single glass envelope, allowing it to serve more than one lighting function simultaneously.
It operates on a 12-volt electrical system and draws 21 watts on its high-intensity filament and 5 watts on its low-intensity filament.
The 1157 uses a BAY15d bayonet base, which features two offset pins at different heights to prevent incorrect insertion into the socket.
The 1157 conforms to ANSI standards and is recognized in both the United States and Canada, placing it within a widely distributed specification category.
Because the same bulb number applies to both the front and rear turn signal positions on the WIA, a single bulb type serves both locations on the vehicle.
The BAY15d base is not universally interchangeable with other bayonet base types, such as the single-pin BA15s, and substitution with physically similar but electrically different bulbs risks incorrect function or socket damage.