The White/GMC WG front and rear turn signal bulbs both utilize a 1157 size bulb for proper operation. The replacement chart covers vehicle production spanning 1990 to 1995 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 1157 is the sole bulb type specified for the White/GMC WG across all listed turn signal positions and model years.
The 1157 is a dual-filament bulb, meaning it contains two separate filaments within a single envelope, allowing it to serve two distinct lighting functions at different wattages.
It operates on a 12-volt electrical system and draws 21 watts on its primary filament and 5 watts on its secondary filament.
The 1157 uses a BAY15d bayonet base, which is an offset twin-pin mount. The two pins are positioned at different heights to ensure the bulb is inserted in the correct orientation, preventing filament misalignment.
The 1157 conforms to ANSI standards and is recognized in both the United States and Canada, reflecting a standardized specification shared across North American markets.
The front turn signal position on the WG uses the 1157 across the 1990-1995 model years.
The rear turn signal position on the WG also uses the 1157 across the same 1990-1995 span, making the front and rear positions interchangeable in terms of bulb fitment.
Because the BAY15d base uses offset pins, substituting a single-pin or symmetrical twin-pin base bulb would result in an incompatible fit, even if the physical envelope size appeared similar.