Buick GS 400 front side marker bulbs use 194NA size while rear side marker bulbs use 194 size. The replacement chart covers 1968 to 1969 production 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 Buick GS 400 uses two bulb types across its side marker positions: the 194NA for front side markers and the 194 for rear side markers, both covering the 1968-1969 model years.
Both the 194NA and 194 are T10 miniature wedge bulbs operating at 12 volts and 3.78 watts, conforming to ANSI standards recognized in the United States and Canada.
The T10 wedge form factor uses a wedge-shaped base rather than a pin or bayonet mount, with the base itself acting as the electrical contact when pressed into a compatible socket.
The 194NA and 194 share identical voltage, wattage, and base type, with the sole distinction being that the 194NA incorporates natural amber-tinted glass in its envelope.
The natural amber glass of the 194NA produces a filtered amber output without relying on a colored lens, which is why it is specified for the front side marker position on the Buick GS 400 rather than the clear 194.
Because the 194NA and 194 share the same T10 wedge base and electrical ratings, the two types are physically interchangeable in terms of socket fit, though substituting a 194 in a front side marker position would alter the color output of that lamp.