Alfa Romeo 4C front inner turn signal requires PY24WNA bulb size while rear turn signal uses P21W bulb size. The chart covers 2015 to 2020 production years with replacement bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Alfa Romeo 4C uses the PY24WNA bulb for the front inner turn signal across all model years from 2015-2020.
The PY24WNA is an ANSI-standard bulb rated at 12V and 24W, designed for use in the United States and Canada. It uses a PGU20-4 base and is the amber-tinted variant of the ECE-standard PY24W.
The PGU20-4 base on the PY24WNA is a wedge-pin type specific to this bulb family. The ECE version, PY24W, shares the same wattage and voltage rating but uses a different base configuration, making the two types physically non-interchangeable despite their similar designations.
The rear turn signal on the Alfa Romeo 4C uses the P21W bulb across all model years from 2015-2020.
The P21W is an ECE-standard single-filament bulb rated at 12V and 21W. It uses a BA15s bayonet base, which is a single-contact bayonet fitting with offset pins to ensure correct orientation during installation.
The front inner turn signal draws 24W while the rear turn signal draws 21W, meaning the two positions are not electrically equivalent and the bulb types are not interchangeable between positions.
The PY24WNA and P21W operate on the same 12V supply, which is standard for automotive electrical systems, though their wattage ratings and base types differ entirely.