Plymouth Sapporo high beam headlight bulbs use H4651 size while low beam headlight bulbs use H4656 or H4652 sizes. The replacement chart covers 1978 through 1983 vehicle 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 Plymouth Sapporo uses sealed beam headlight units across its entire production run of 1978-1983, meaning the lens, reflector, and filament are fused into a single glass assembly that is replaced as a complete unit rather than accepting a separate replaceable bulb.
All three headlight types specified for the Sapporo, the H4651, H4656, and H4652, conform to ANSI standards recognized in both the United States and Canada, and all operate on a 12-volt electrical system.
Each of the three sealed beam types follows the 4x6-inch rectangular form factor, which was a standardized size widely used in North American vehicle lighting regulations of that era.
The H4651 sealed beam serves as the high beam headlight for the Plymouth Sapporo across all model years from 1978-1983, making it the only high beam unit specified for this vehicle throughout its full production span.
The H4652 is described as a variant of the H4651 and was fitted as the low beam headlight in the 1978 and 1981 model years, while the H4656 filled the low beam position in 1979-1980 and 1982-1983.
Because the H4651 and H4652 share a variant relationship and occupy the same 4x6-inch rectangular housing format, substitution between them without confirming the correct ANSI designation for the intended beam position carries a fitment risk.