Mercury Caliente Map Light Bulb Size

Additional Notes

• The Mercury Caliente map light specifications cover the 1964-1967 model years, with three distinct bulb types used across that span.
• The 1895 bulb is a miniature wedge type rated at T5, operating at 12V and 0.9W, and it serves the 1964-1965 Mercury Caliente map light position.
• The T5 designation on the 1895 refers to a tubular bulb form factor approximately 5/8 of an inch wide, a common sizing convention in ANSI miniature bulb classification.
• The 1816 bulb fitted to the 1966 model is also a miniature wedge type, though it carries a T3.25 form factor and a notably higher 4W rating compared to the 1895 used in prior years.
• The T3.25 designation on the 1816 indicates a slightly narrower tubular profile than the T5, despite the 1816 drawing more wattage, which reflects differences in filament and envelope design rather than physical size alone.
• The 1967 Mercury Caliente map light uses the 631 bulb, a single-filament type with a BA15s bayonet base rated at 12V and 21W, making it substantially higher in wattage than the bulbs specified for any other year in this application.
• The BA15s base on the 631 is a single-contact bayonet fitting with a 15mm collar, and it is noted as a variant of the 1156 bulb, meaning the two share base and voltage compatibility but may differ in other rated values.
• All three bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada.
• The wedge base design of the 1895 and 1816 bulbs requires no separate metal base, as the glass envelope itself forms the contact points, which is a key fitment distinction from the bayonet-based 631.
• Because the 1964-1965, 1966, and 1967 model years each use a different bulb type with different base configurations, the map light bulbs across these four years are not interchangeable.