Mercury Cyclone Dome Light Bulb Size

Mercury Cyclone dome light bulb sizes 105 and 1003 are specified in this replacement chart. The data covers vehicle production years spanning 1964 to 1971.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1970-1971	105
1964-1969	1003

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 13W.	105
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1003

Other Locations

Additional Notes

The 1003 bulb is the most frequently specified dome light bulb for the Mercury Cyclone, covering the 1964-1969 model years across six consecutive years of production.
Both bulb types found in the Mercury Cyclone dome light specifications, the 105 and the 1003, are ANSI-standardized components recognized in the United States and Canada.
The 105 and 1003 bulbs share the same BA15s single-contact bayonet base, a base type characterized by a 15mm barrel with a single pin on its side.
Despite sharing the same base type, the 105 and 1003 are not interchangeable, as the 105 operates at 13W while the 1003 operates at a notably higher 21W on the same 12V circuit.
The 1970-1971 model years use the 105 bulb, which draws less wattage than the 1003 unit specified for earlier production years.
The 105 bulb is noted as a variant of the 1156, a widely produced automotive bulb, which indicates broad availability of compatible replacements within the BA15s single-filament family.
Both bulb types operate on a 12-volt electrical system, consistent with the standard automotive electrical architecture of the era.