turn signal rapid flash
 

2005 Saturn Vue 3.5L Replaced front right side non working turn signal bulb with a Sylvania 3457A, old bulb was a 3457AK. Now right turn signal flashes very rapidly. Could this be the bulb or something else?

Yes, there are differences between those bulbs. Replace with what was in there.

Don't quote me, but I was trying to research this . I think the a is an incandescent bulb and the other one is an LED bulb or something to that effect, The turn signal circuitry behaves differently because the wrong bulb does not have the same electrical characteristics as the correct one

The difference in the bulbs is terminal location. They have moved the grounds around and should have renumbered the bulb completely.

The 'A' indicates that the bulb has an amber coating. The 1157A is identical to the 1157 except it is amber. This came about way back when, and it was cheaper to change the bulb than to change the plastic (some glass) lenses for front parking/turn signal lights.