Plymouth Horizon Dome Light Bulb Size

Additional Notes

• The Plymouth Horizon dome light specifications cover model years 1978-1990, with two distinct bulb types appearing across that span: the 211-2 and the 912.
• The 211-2 is a festoon-style bulb with a 41mm length and an SV8.5 base, operating at 12V and 12W under the ANSI standard applicable in the US and Canada.
• A festoon bulb is held in place by spring-loaded end caps rather than a socket, making its physical length a critical fitment factor.
• The SV8.5 base designation on the 211-2 refers to a cylindrical contact base with a width of 8.5mm, which determines socket compatibility.
• The 912 is a wedge-style bulb of the T15 form factor, also rated at 12V and 12W and conforming to the same ANSI standard.
• A wedge bulb uses its own glass envelope pinched at the base to make electrical contact, requiring no separate metal base or socket pins.
• The 912 is listed as a variant of the 921, meaning the two share the same T15 wedge form factor and voltage rating, though they are not identical and should not be treated as direct substitutes without confirming wattage compatibility.
• The Plymouth Horizon used the 912 wedge bulb for the dome light in model years 1980-1981, while all other listed years used the 211-2 festoon bulb.
• Because the 211-2 and 912 are physically different bulb types, one cannot be substituted for the other without a compatible replacement socket or adapter.
• Both bulb types share the same 12V, 12W electrical rating, meaning the difference between model years is one of physical form factor rather than power draw.