Fiat 500X front and rear turn signal bulbs use 7440NA and P21W sizes. The chart contains bulb size specifications across the 2016 to 2023 production range.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 7440NA is a single-filament wedge bulb using the T20 base type, rated at 12V and 21W. It is built to the ANSI standard used in the United States and Canada, and its natural amber glass produces the orange color required for turn signal applications without relying on a colored lens or housing.
The P21W is a single-filament signalling bulb rated at 12V and 21W, built to the ECE standard used in Europe and worldwide. It uses a BA15s bayonet base, which is a single-contact bayonet fitting, making it physically incompatible with the T20 wedge socket used by the 7440NA despite both bulbs sharing the same wattage.
Although the 7440NA and P21W share identical voltage and wattage ratings, their base types differ entirely. The T20 wedge and BA15s bayonet fittings are not interchangeable, so one bulb cannot be substituted for the other without a socket adapter or housing modification.
The Fiat 500X front turn signal uses the 7440NA for the 2016-2020 and 2022-2023 model years. The 2021 model year is the sole exception within this position, where the P21W is specified instead.
The rear turn signal of the Fiat 500X uses the 7440NA for the 2019-2020 model years and the P21W for the 2016-2018 model years, indicating a base type change between the 2018 and 2019 model years for that position.
The 2021 Fiat 500X front turn signal specifies the P21W, which follows the ECE standard. This contrasts with the surrounding model years for the same position, all of which specify the ANSI-standard 7440NA.
Both bulb types specified across all positions and years operate at 12V, which is consistent with standard 12-volt automotive electrical systems.