Merkur XR4Ti License Plate Bulb Size

The Merkur XR4Ti license plate light requires a 1816 bulb size for proper illumination of the rear registration area. Data for the specified component covers the period from 1985 through 1989.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1985-1989	1816

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T3.25). 12V, 4W.	1816

Other Locations

Additional Notes

The Merkur XR4Ti uses the 1816 bulb for its license plate lighting across the full 1985-1989 production run.
The 1816 is an ANSI-standardized bulb, meaning its specifications are governed by a recognized North American standard shared across the United States and Canada.
The 1816 bulb belongs to the T3.25 form factor, which denotes a tubular miniature wedge-base design. The T designation refers to the tubular shape, and the 3.25 figure represents the width in eighths of an inch.
A wedge-base bulb has no metal pins or a separate base cap. Instead, the glass envelope itself is pinched flat at the bottom and held in place by friction within the socket.
The 1816 operates at 12 volts, which is consistent with standard automotive electrical systems.
At 4 watts, the 1816 draws a low level of power, typical for a license plate application where output requirements are modest.
Because the 1816 uses a wedge base, fitment depends on socket size and shape rather than a keyed pin configuration. A replacement bulb must match the T3.25 wedge profile to seat correctly in the XR4Ti's license plate socket.
The single bulb size across all five model years indicates that no socket or housing revision occurred during the XR4Ti's production that would affect bulb compatibility.