The Isuzu NQR headlight bulb size specifications include 9003 and H4651 for high beam applications and 9003 and H4656 for low beam applications. The replacement chart covers vehicle production years from 1996 through 2013 with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Isuzu NQR (Tilt Cab) uses two distinct headlight technologies across its model range. Units from 1996-2005 use sealed beam assemblies, while those from 2006-2013 use a replaceable halogen bulb format.
The 9003 is a dual-filament halogen bulb rated at 12V with a 60W high beam filament and a 55W low beam filament, mounted on a P43t base. A single 9003 bulb serves both the high beam and low beam positions in the 2006-2013 NQR Tilt Cab.
The H4651 and H4656 are both 4x6-inch rectangular sealed beam units operating at 12V. Unlike the 9003, neither contains a replaceable bulb element; the entire sealed unit is the serviceable component.
The H4651 fills the high beam position and the H4656 fills the low beam position on the 1996-2005 NQR Tilt Cab. Although both share the same 4x6-inch rectangular form factor, they are not interchangeable between positions.
All three bulb types, the 9003, H4651, and H4656, conform to ANSI standards recognized in both the United States and Canada.
The transition from sealed beam units to the 9003 halogen format occurred between the 2005 and 2006 model years across both the high beam and low beam positions simultaneously.
Because the H4651 and H4656 are sealed beam units, a failure in either requires replacement of the full assembly rather than an internal bulb element, which distinguishes the service procedure from that of the 9003-equipped models.
All specifications listed apply exclusively to the Tilt Cab body configuration of the NQR across the entire 1996-2013 range covered.