The Volkswagen Golf Alltrack turn signal requires a 7440NA bulb size for the lighting assembly. Data for the specific bulb requirements covers the period from 2018 through 2018.
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 in the T20 form factor, rated at 12V and 21W. Its natural amber glass produces the required amber turn signal color without relying on a colored lens or socket filter.
The H21W follows the ECE standard used in Europe and worldwide markets. It shares the same 12V, 21W electrical rating as the 7440NA but uses a BAY9s bayonet base, making the two bulbs physically incompatible with each other despite their identical wattage.
The 12174NA is an OEM part number designation rather than an ANSI or ECE standard code. It is a natural amber glass variant rated at 12V, and it serves the same front turn signal function as the H21W in halogen capsule headlamp configurations for 2017-2018 models.
On the Volkswagen Golf Alltrack, the front turn signal bulb type is determined by the headlamp system installed. The 2017-2018 model years require either the 12174NA or the H21W depending on whether the vehicle is fitted with halogen capsule headlamps or HID headlamps respectively.
The 2019 Golf Alltrack front turn signal specification shifts to the 7440NA for halogen capsule headlamp configurations, replacing the 12174NA used in the same configuration for 2017-2018.
The rear turn signal on the Golf Alltrack uses the 7440NA for the 2017-2018 model years, with no headlamp-dependent variants listed for that position.
Because the H21W uses a BAY9s base and the 7440NA uses a wedge base, these bulbs require different sockets entirely. Substituting one for the other is not physically possible without modifying the socket.