Seagrave Fire Apparatus J headlight bulbs utilize H4651 size for high beam and H4652 or H4656 sizes for low beam applications. The replacement chart covers vehicle production spanning 1989 to 2004.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Seagrave Fire Apparatus J uses H4651, H4652, and H4656 bulbs across its headlight positions. All three are ANSI-standardized sealed beam units operating at 12V and sharing the same 4x6-inch rectangular form factor.
Sealed beam units are self-contained assemblies in which the filament, reflector, and lens are fused into a single housing. When a filament fails, the entire unit is replaced rather than an internal bulb component.
The H4651 is the sole high beam specification for the Seagrave Fire Apparatus J across all model years from 1989-2004, with no variation across that span.
The low beam position does not follow the same uniformity. Both H4652 and H4656 appear across the 1989-2004 model year range, with the specific unit varying by year.
Although H4651 and H4652 are described as variants of the same 4x6-inch rectangular sealed beam standard, they are designated for different beam positions and are not interchangeable between high and low beam applications.
H4656 is specified for the low beam position in 1989-1993, 1995-1997, and 2001-2002 model years of the J, while H4652 fills the low beam role in the remaining years within that range.
All three sealed beam types conform to ANSI standards recognized in both the United States and Canada, placing them within a widely adopted North American specification framework for rectangular headlight units.
Because H4652 and H4656 share the same physical format and voltage rating yet carry distinct ANSI designations, substituting one for the other in the low beam position would not align with the year-specific fitment data provided for the J.