Volkswagen GTI Dome Light Bulb Size

Additional Notes

• The Volkswagen GTI uses three distinct dome light bulb types across its model years: the 12961, DE3423, and 6411.
• The 12961 is a Philips part number designating a miniature wedge bulb in the T10 form factor, fitted with a W2.1x9.5d base and rated at 12V, 5W.
• The DE3423 and 6411 are both ANSI-standard festoon bulbs, a format that uses flat end-cap contacts rather than a pin or wedge base, making them physically incompatible with the T10 socket used by the 12961.
• The DE3423 has a 41mm length, while the 6411 measures 36mm. Because festoon bulbs rely on spring tension between two contact points, length is a critical fitment factor, and these two types are not interchangeable with each other.
• The 6411 carries an SV8.5 base designation, which refers to its contact cap style, and is rated at 12V, 5W, matching the wattage of the 12961 despite the different socket type.
• The Volkswagen GTI (2006-2009) uses the 6411 bulb for its dome light, representing the earliest generation covered in these specifications.
• The DE3423 applies to the 2010-2014 model years, spanning a five-year period during which the GTI transitioned away from the 6411 festoon format.
• The 12961 T10 wedge bulb is specified for the 2015-2016 and 2020-2021 model years, with the 2021 entry noting it serves both front and rear dome light positions.
• The shift from festoon to wedge base formats across generations indicates socket design changes in the GTI interior lighting system, meaning bulb substitution across these groups is not supported by the specifications.
• The DE3423 carries no listed wattage rating in these specifications, whereas both the 12961 and 6411 are rated at 5W.