The Ford C-Max tail light utilizes a 1157 bulb size for the specific lighting component located at the rear of the vehicle. Data for the bulb covers the range from 2013 to 2016.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford C-Max tail light specifications cover the 2013-2018 model years across two positions: the inner tail light and the outer tail light.
The outer tail light position uses the 7443 bulb across all six model years, from 2013 through 2018, without variation.
The 7443 is an ANSI-standard dual-filament wedge bulb in a T20 form factor, rated at 12V with a 21W/5W filament configuration, where the higher wattage serves the brake or turn function and the lower wattage serves the running light function.
The inner tail light position of the Ford C-Max uses two different bulb types depending on the model year, with the 1157 fitted in 2013-2016 and the 12961 fitted in 2017-2018.
The 1157 is an ANSI-standard dual-filament bulb with a BAY15d bayonet base, rated at 12V and 21W/5W, making it functionally similar in wattage output to the 7443 used in the outer position.
The 12961 is a Philips part number designating a miniature wedge bulb in a T10 form factor with a W2.1x9.5d base, rated at 12V and 5W, which is a single-filament low-wattage bulb distinct from the dual-filament types used elsewhere in the C-Max tail light system.
The base types across these three bulbs are not interchangeable. The BAY15d bayonet base of the 1157, the W2.1x9.5d wedge base of the 12961, and the T20 wedge base of the 7443 each require their own socket, preventing cross-position substitution.
The shift from the 1157 to the 12961 in the inner tail light position between the 2016 and 2017 model years represents a significant change in bulb wattage, from a 21W/5W dual-filament unit to a 5W single-filament unit.
The 1157 and 7443 share the same 12V, 21W/5W electrical ratings, but their base types differ, as the 1157 uses a BAY15d bayonet fitting while the 7443 uses a wedge-style T20 fitting, so they are not physically interchangeable despite matching wattage.
Owners of 2013-2016 C-Max models sourcing inner tail light replacements should note that the 1157 is an ANSI-standard bulb widely available across the US and Canadian markets, while the 12961 used in 2017-2018 models is identified by a Philips-specific part number.