Freightliner Cascadia Map Light Bulb Size

The Freightliner Cascadia map light requires a 12821 bulb size for proper installation and function within the interior overhead lighting system. Available data covers the range from 2008 through 2017 for the specified vehicle components.

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
2008-2017	12821

Bulb Specifications

Description	Bulb Size
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12821

Other Locations

Additional Notes

The Freightliner Cascadia map light uses the 12821 bulb across all listed model years from 2008-2017.
The 12821 is a Philips part number designating a miniature wedge bulb in the T10 form factor, which refers to the tubular glass envelope with a 10mm width.
The bulb operates on a W2.1x9.5d base, a wedge-type base where the electrical contacts are formed directly into the plastic wedge rather than through a separate metal fitting.
The 12821 is rated at 12 volts and 5 watts, placing it in the low-wattage category typical of interior cabin lighting applications.
The T10 wedge format is a widely used standard, meaning the 12821 is cross-compatible with other bulbs sharing the same W2.1x9.5d base and 12V/5W rating, provided the physical fit within the socket is confirmed.
Because the 12821 designation is specific to Philips, equivalent bulbs from other manufacturers are identified by different part numbers despite sharing the same T10 wedge base and electrical specifications.