GMC Topkick front and rear side marker bulbs require 194 size bulbs for proper illumination. The replacement chart covers 1990 to 2001 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC Topkick uses the 194 bulb for both front and rear side marker positions across the 1990-2001 model years.
The 194 is an ANSI-standardized bulb type, meaning its specifications are governed by a recognized industry standard applicable in both the United States and Canada.
This bulb belongs to the T10 miniature wedge family, a form factor defined by a wedge-shaped base that seats directly into a socket without a separate metal base or pins.
The 194 operates at 12 volts, which is consistent with standard automotive electrical systems.
At 3.78 watts, the 194 draws relatively low power, a characteristic typical of small marker and courtesy light applications.
The identical bulb size across both front and rear side marker positions on the GMC Topkick means a single bulb type serves both locations on the vehicle.
T10 wedge bulbs are a widely produced form factor, and the 194 designation is interchangeable with certain other bulbs in the same family, though voltage and wattage ratings should be confirmed before substitution to avoid socket or circuit incompatibility.
The consistency of the 194 specification across all twelve model years covered indicates no mid-cycle changes to the side marker bulb fitment during the 1990-2001 production span of the Topkick.