Volkswagen Quantum front turn signal bulbs utilize a P21/5W size while rear turn signal bulbs require a P21W size. The replacement chart covers 1982 through 1988 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Volkswagen Quantum uses two distinct bulb types across its turn signal positions: the P21/5W at the front and the P21W at the rear, both governed by ECE standards recognized in Europe and worldwide. This split applies uniformly across the 1982-1988 model years.
The P21/5W is a dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament. Its dual-filament design makes it suitable for positions that serve more than one lighting function simultaneously.
The P21/5W uses a BAY15d bayonet base. The BAY15d designation indicates an offset pin configuration, which physically prevents the bulb from being seated incorrectly and ensures the two filaments align with their intended circuits.
The Volkswagen Quantum front turn signal requires the P21/5W across all 1982-1988 model years, meaning the BAY15d socket is the correct base type for that position throughout the entire production run covered by these specifications.
The P21W is a single-filament bulb rated at 12V and 21W. Unlike the P21/5W, it carries no secondary filament, making it suited for positions dedicated to a single lighting function.
The P21W uses a BA15s bayonet base. The BA15s features symmetrically placed pins, which distinguishes it from the offset BAY15d base of the P21/5W. The two bases are not interchangeable despite their similar appearance.
Because the front and rear turn signal positions use different base types, BAY15d for the front and BA15s for the rear, substituting one bulb for the other is not physically compatible without modification to the socket.
Both the P21/5W and P21W share the same 21W primary wattage rating, which means the current draw on the turn signal circuit is consistent between the front and rear positions at full operating load.