The GMC PM252 front and rear turn signal bulbs both utilize a 1129 size bulb for proper operation. The replacement chart covers vehicle production spanning 1952 to 1955 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 GMC PM252 uses the 1129 bulb across both its front and rear turn signal positions for the 1952-1955 model years.
The 1129 is an ANSI-standardized bulb type, meaning its physical and electrical specifications conform to a defined industry standard recognized in both the United States and Canada.
The 1129 is a dual-filament bulb, which means it contains two separate filaments within a single envelope, allowing it to serve more than one lighting function.
The 1129 uses a BAY15d bayonet base, a two-pin offset base design where the two pins are positioned at different heights to ensure the bulb can only be inserted in one orientation, preventing incorrect filament alignment.
The 1129 operates at 12 volts with a wattage rating of 21/5W, where the higher wattage corresponds to the brighter filament and the lower wattage to the dimmer filament.
The 1129 is described as a variant of the 1157, a widely used automotive bulb that shares the same BAY15d base and dual-filament configuration, though the two types are not necessarily interchangeable due to potential differences in wattage or filament positioning.