Peterbilt 337 Map Light Bulb Size

The Peterbilt 337 map light uses a 912 bulb size for interior illumination. Replacement specifications in the chart span 2010 to 2017 production years.

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
2010-2017	912

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). Variant of 921. 12V, 12W.	912

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Additional Notes

The 912 is the sole map light bulb size listed for the Peterbilt 337 across the 2010-2017 model years.
The 912 bulb follows the ANSI standard, meaning it conforms to a recognized North American specification used in both the United States and Canada.
It belongs to the T15 form factor, which refers to a tubular bulb body roughly 15/8 of an inch wide, fitted with a wedge-style base rather than a pin or bayonet mount.
The wedge base design means the bulb is held in place by the socket walls gripping the base directly, with no separate locking mechanism required.
The 912 operates at 12 volts and consumes 12 watts, placing it in the range typical of low-output interior lighting applications.
The 912 is noted as a variant of the 921 bulb. While the two share the same T15 wedge form factor and voltage rating, the 921 operates at a higher wattage of 18 watts, making the two bulbs non-identical despite their physical similarity.
Because the 912 and 921 share the same physical base and socket type, a 921 may fit the Peterbilt 337 map light socket mechanically, but the wattage difference means it would draw more current than the original specification calls for.