Seagrave Fire Apparatus W models utilized H4651 bulbs for high beam headlights and H4656 bulbs for low beam headlights, with each bulb size engineered for specific lighting functions. The replacement chart covers 1988 to 1989 production years and documents headlight bulb specifications for these fire apparatus vehicles.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Seagrave Fire Apparatus W uses the H4651 for high beam and the H4656 for low beam across the 1988-1989 model years, with each position requiring a distinct sealed beam unit.
Both the H4651 and H4656 are 4x6-inch rectangular sealed beam units governed by ANSI standards recognized in the United States and Canada.
A sealed beam unit integrates the filament, reflector, and lens into a single non-serviceable assembly, meaning the entire unit is replaced rather than an internal bulb.
Both units operate on a 12V electrical system, which is standard for automotive and light commercial applications of this era.
Because the H4651 and H4656 share the same physical 4x6-inch rectangular form factor, the distinction between high and low beam function is carried by the bulb type designation rather than housing size, making correct type selection critical during replacement.
The ANSI standardization of both units means physically compatible replacements from different manufacturers are generally available, provided the correct H-series designation is matched to the intended beam position.