Mercedes-Benz 240D Dome Light Bulb Size

Additional Notes

• The Mercedes-Benz 240D uses the 6411 bulb size for the dome light across all listed model years, spanning 1974-1983.
• The 6411 is an ANSI-standardized bulb designation, meaning it conforms to a defined set of electrical and physical specifications recognized across the United States and Canada.
• The 6411 is a festoon-style bulb, a cylindrical form factor that mounts by pressing its two end caps into spring clips rather than using a twist or plug-in socket.
• The 6411 bulb has a length of 36mm, which is the critical fitment factor for festoon bulbs, as the spring clip housing must match this length to hold the bulb securely.
• The 6411 uses an SV8.5 base, a designation that refers to the 8.5mm cap width on each end of the festoon body, and any replacement bulb must share this base specification to seat correctly.
• The 6411 operates at 12 volts, consistent with the standard electrical system voltage found in passenger vehicles of this era.
• The 6411 is rated at 5 watts, placing it in the low-wattage category typical of interior courtesy lighting, where prolonged illumination without significant battery drain is a design consideration.
• When sourcing a replacement, both the 36mm length and the SV8.5 base must be matched simultaneously, as festoon bulbs with different lengths or cap widths are not interchangeable even if the voltage and wattage ratings are identical.