Hummer H3 Map Light Bulb Size

The Hummer H3 map light requires a 578 bulb size for proper installation and function within the interior overhead lighting housing. Data for the specific component covers the period from 2006 through 2010.

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
2006-2010	578

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V, 12W.	578

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Additional Notes

The 578 bulb is the map light bulb size for the Hummer H3 across the 2006-2010 model years.
The 578 is a festoon-type bulb, meaning it is cylindrical in shape and makes electrical contact through metal caps at each end rather than through a base socket.
The 578 bulb has a length of 41mm, which is the critical fitment factor for festoon bulbs, as the housing span must match this length for the end-cap contacts to seat correctly.
The bulb operates at 12 volts and draws 12 watts, which is consistent with standard automotive interior lighting circuits.
The 578 designation follows the ANSI standardization system, meaning it is a recognized specification in both the United States and Canada.
Festoon bulbs of different lengths are not interchangeable even when voltage and wattage ratings match, as an incorrect length will prevent proper contact or cause fitment stress on the housing.