The Volkswagen Quantum brake light requires a P21W bulb size for proper installation and function within the rear lighting assembly. Data for the specified component covers the period from 1982 through 1988.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Volkswagen Quantum uses the P21W bulb for brake lighting across all documented model years, spanning 1982-1988.
The P21W is an ECE-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base, a single-contact base type widely used in European and international automotive applications.
The BA15s designation indicates a single-contact bayonet cap with a 15mm base, distinguishing it from the dual-contact BA15d variant. The two are not interchangeable despite sharing the same physical base size.
The Center High Mount Stop Light on the Volkswagen Quantum uses the 12961 bulb across all documented model years, spanning 1982-1988.
The 12961 is a Philips part number referencing a T10 miniature wedge bulb rated at 12V and 5W, fitted with a W2.1x9.5d wedge base.
The W2.1x9.5d base is a wedgeless, friction-fit type where the bulb is held in place by its glass envelope rather than a locking mechanism, making it incompatible with bayonet or screw-base sockets.
The P21W and 12961 serve distinct functions within the brake lighting system. The P21W handles primary stop light output at 21W, while the 12961 operates the high-mount position at a significantly lower 5W output.
Substituting a dual-filament P21/5W bulb in place of the P21W is not supported by these specifications, as the Quantum brake circuit calls for a single-filament unit only.