Honda Motorcycle VT1100C Shadow Turn Signal Bulb Size
Honda Motorcycle VT1100C Shadow front turn signal bulbs measure 1034 in size, while rear turn signal bulbs measure P21W or 1073 in size. The replacement chart covers 1985 to 2007 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 Honda Motorcycle VT1100C Shadow uses two distinct bulb types across its front and rear turn signals: the 1034 for all front positions and either the P21W or 1073 for rear positions, depending on the model year.
The 1034 bulb is an ANSI-standard dual-filament bulb rated at 12V and 21/5W, fitted with a BAY15d bayonet base. Its dual-filament design means it carries two separate circuits within a single envelope, a characteristic that distinguishes it from single-filament alternatives.
The front turn signal position on the Honda Motorcycle VT1100C Shadow uses the 1034 bulb without variation across the 1985-2007 model range covered in the specifications.
The BAY15d base of the 1034 is not interchangeable with the BA15s base found on both the P21W and 1073 bulbs. The offset pins on a BAY15d base serve to orient the dual filaments correctly, while the BA15s base uses a single-filament configuration with a simpler pin arrangement.
The P21W is an ECE-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base. It is widely used in European and international markets and carries the same wattage on its single filament as the higher-draw filament of the 1034.
The 1073 is an ANSI-standard single-filament bulb rated at 12V and 13W, also fitted with a BA15s bayonet base. It is described as a lower-wattage variant of the 1156, drawing notably less power than the P21W despite sharing the same base type.
Because the P21W and 1073 share a BA15s base, their housings are physically compatible, but their wattage ratings differ significantly at 21W versus 13W. Substituting one for the other in a circuit calibrated for a specific draw could affect turn signal flash rates or trigger hyperflash conditions.
The rear turn signal on the VT1100C Shadow used the 1073 bulb in 1985, then the P21W in 1986-1987, then reverted to the 1073 in 1988-1990 and 1992, before settling on the P21W from 1993 onward through 2007.
The 1034 is described in the specifications as a variant of the 1157. The 1157 is a widely recognized ANSI dual-filament bulb, and the 1034 shares its BAY15d base and general construction while operating at the same 12V and 21/5W ratings.
Front and rear turn signal positions on the VT1100C Shadow require different base types throughout the model range, as the front consistently uses the BAY15d-based 1034 while all rear bulbs across all listed years use the BA15s base, making the two positions non-interchangeable.