The Merkur XR4Ti front turn signal bulb uses a 1157 size, while the rear turn signal bulb uses a 1156 size. The replacement chart covers vehicle production spanning 1985 to 1989 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 Merkur XR4Ti uses the 1157 bulb for the front turn signal across all model years from 1985-1989.
The 1157 is a dual-filament bulb, meaning it serves two lighting functions within a single housing, operating at 21W on the primary filament and 5W on the secondary filament.
The 1157 uses a BAY15d bayonet base, which features two offset pins at different heights to prevent incorrect installation of the bulb into the socket.
The rear turn signal on the XR4Ti uses the 1156 bulb across all model years from 1985-1989.
The 1156 is a single-filament bulb rated at 21W, dedicated to one lighting function rather than the dual-purpose role of the 1157.
The 1156 uses a BA15s bayonet base, which has two pins at equal heights, distinguishing it physically from the BAY15d base of the 1157.
Both the 1157 and 1156 operate at 12V, consistent with standard automotive electrical systems.
Both bulb types conform to ANSI standards applicable in the United States and Canada.
The 1157 and 1156 share the same 15mm bayonet base width, but their pin configurations differ, making them non-interchangeable between front and rear sockets despite their physical similarity.