GMC P15 and P1500 front and rear turn signal bulbs utilize 1156, 199, or 1073 bulb sizes depending on model configuration. The replacement chart covers 1967 through 1972 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 three bulb types specified across the GMC P15 / P1500 turn signal positions are the 1156, 199, and 1073, all of which are ANSI-standardized single-filament bulbs rated at 12 volts and sharing the BA15s bayonet base.
The BA15s bayonet base is a single-contact design, which is physically distinct from the dual-contact BA15d base. This distinction is relevant when sourcing replacements, as the two base types are not interchangeable despite their similar appearance.
The 1156 is the most frequently specified bulb across both the front and rear turn signal positions throughout the 1967-1972 model range, operating at 12V and 21W.
The 199 is described as a variant of the 1156, sharing the same 12V and 21W rating along with the BA15s base, which indicates a high degree of electrical compatibility between the two types.
The 1073 is a lower-wattage variant of the 1156, rated at 13W rather than 21W. This difference in wattage means the 1073 produces less light output and draws less current than the 1156 or 199.
Because the 1073 draws significantly less current than the 1156 or 199, substituting a higher-wattage bulb in a position originally specified for the 1073 could affect turn signal flash rate, as most conventional flasher relays are current-dependent.
The front and rear turn signal positions on the GMC P15 / P1500 do not consistently use the same bulb type within a given model year. For example, the 1972 model uses a 1156 at the front and a 199 at the rear.
The 1967 model year is the only year in the specifications where the 1073 appears, with the front position using the 1073 and the rear using the 1156.
The 199 appears in the front turn signal position for the 1969-1970 model years and in the rear turn signal position for the 1970 and 1972 model years.
All three bulb types conform to ANSI standards applicable in both the United States and Canada, indicating they were designed to meet the same regulatory and performance criteria across both markets.