Mercury Cougar Dome Light Bulb Size

Additional Notes

• Three distinct bulb types appear across the Mercury Cougar dome light specifications: the 211-2, the 912, and the 561, all rated at 12 volts and 12 watts under the ANSI standard applicable to the United States and Canada.
• The 912 is the most frequently specified bulb across these records, covering model years 1980 and 1983-1997.
• The 912 is a T15 wedge-type bulb, meaning it uses a wedge-shaped plastic base rather than a metal contact base, and it is classified as a variant of the 921 bulb.
• Although the 912 and 921 are closely related, they are not identical, and substituting one for the other without confirming electrical and physical compatibility may result in an improper fit.
• The 211-2 is a festoon-style bulb with an SV8.5 base and a 41mm length, specified for the Mercury Cougar in 1967-1973 and 1999-2002.
• The 561 is also a festoon-style bulb but uses end-cap contacts rather than an SV8.5 base, and its length is 44mm, making it physically distinct from the 211-2 despite both being festoon types.
• The 3mm length difference between the 211-2 and the 561 means the two festoon bulbs are not interchangeable, as festoon holders are sized to match a specific bulb length.
• The 561 is specified for model years 1974-1979, representing a period between two separate spans that use the 211-2.
• All three bulb types share the same voltage and wattage rating of 12V and 12W, so the distinctions between them are physical and base-type rather than electrical output.
• The SV8.5 base of the 211-2 refers to a bayonet-style festoon cap with a specific cap width, which determines socket compatibility independently of bulb length.