The GMC K15 Suburban front and rear turn signal bulb sizes include 198, 1156, 1073, and 199 configurations across different model variations. The replacement chart covers 1967 through 1978 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 GMC K15 Suburban uses three distinct bulb types across its front and rear turn signal positions for the 1967-1978 model years: the 198, 1156, and 1073 for both positions, with the 1034 appearing exclusively at the front and the 199 exclusively at the rear.
The 198 bulb is the most frequently specified type across these turn signal positions, covering both front and rear locations for the 1973-1978 model years. It is a T5 miniature wedge bulb rated at 12V and 2W, which places it at a significantly lower wattage than the other bulbs in these specifications.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W. It appears across multiple model years in both the front and rear turn signal positions, making it the second most common type in these specifications.
The 1073 is also a single-filament bulb with a BA15s bayonet base, rated at 12V and 13W. It is described as a lower wattage variant of the 1156, meaning the two share the same base type but are not electrically equivalent and are not interchangeable without affecting circuit performance.
The 1034 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V and 21/5W. It is specified only for the front turn signal of the GMC K15 Suburban in 1967. Its BAY15d base differs from the BA15s base used by the 1156, 1073, and 199, making it physically incompatible with sockets designed for those bulbs.
The 199 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, and is described as a variant of the 1156. It appears only in the rear turn signal position for the 1969 model year, while the front turn signal for that same year uses the 1156 instead.
The front and rear turn signal positions share the same bulb type for most model years in these specifications, but 1969 is an exception, where the front uses the 1156 and the rear uses the 199.
The BA15s bayonet base is common to the 1156, 1073, and 199 bulbs. While this base type is physically shared among them, their differing wattage ratings mean substitution between them would alter the electrical load on the turn signal circuit.
The transition from the 1156 to the 198 between the 1972 and 1973 model years represents a shift from a 21W BA15s bayonet-base bulb to a 2W T5 wedge bulb, a substantial reduction in wattage that reflects a change in socket and housing design between those model years.
All bulb types listed in these specifications conform to ANSI standards applicable in both the United States and Canada.