The GMC PM153 front and rear turn signal bulbs utilize either 1073 or 1129 size bulbs as specified in the replacement chart. The chart covers vehicle production spanning 1955 to 1957.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC PM153 uses two distinct bulb types across its front and rear turn signal positions: the 1073 for the 1957 model year and the 1129 for the 1955 model year.
Both the 1073 and 1129 are ANSI-standardized bulbs recognized in the United States and Canada.
The 1073 is a single-filament bulb operating at 12V and 13W, fitted with a BA15s bayonet base, which is a single-contact base with a straight pin alignment.
The 1129 is a dual-filament bulb operating at 12V with a 21/5W output rating, fitted with a BAY15d bayonet base, which is a double-contact base with offset pins to prevent incorrect installation.
The BA15s base of the 1073 and the BAY15d base of the 1129 are physically incompatible with each other, meaning the two bulb types are not interchangeable despite both using bayonet-style bases.
The 1073 is described as a lower wattage variant of the 1156 bulb. While the 1156 typically operates at around 26-27W, the 1073 draws only 13W, which affects light output and circuit load.
The 1129 is described as a variant of the 1157 bulb. The dual-filament design of both the 1129 and 1157 allows a single bulb to serve two separate lighting functions, though wattage ratings between the two differ.
For the 1957 GMC PM153, the same bulb size, 1073, is specified for both the front and rear turn signal positions.
For the 1955 GMC PM153, the same bulb size, 1129, is specified for both the front and rear turn signal positions.