The Isuzu EVR uses an H4651 bulb size for high beam headlights and an H4656 bulb size for low beam headlights. The replacement chart covers vehicle production years spanning 1987 to 1993 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 Isuzu EVR uses the H4651 bulb for high beam headlights and the H4656 for low beam headlights across the 1987-1993 model years, with both positions specifying the Heavy Duty variant.
Both the H4651 and H4656 are sealed beam units conforming to ANSI standards recognized in the United States and Canada, meaning the entire lens-and-filament assembly is a single unit rather than a housing containing a separate replaceable bulb.
The H4651 and H4656 share the same 4x6-inch rectangular form factor and operate at 12 volts, with the distinction between the two types corresponding strictly to their designated beam function rather than physical size or voltage.
Because both types are sealed beam units, a failure of either the high beam or low beam headlight on the EVR requires replacement of the whole sealed assembly rather than an internal bulb element.
The Heavy Duty designation on both the H4651 and H4656 indicates a construction grade intended for more demanding operating conditions, typically involving reinforced filament supports and greater resistance to vibration compared to standard sealed beam equivalents.
The ANSI standardization of the 4x6-inch rectangular sealed beam format means that H4651 and H4656 units from different manufacturers are generally interchangeable within their respective beam positions, provided the Heavy Duty specification is maintained.