轉soccer88給你的鏈接裏的解決辦法，但是有點費事，既然燈亮實際也無需改動

Normally when you flip your turn signal switch, the light blinks at a set, slow pace. However, if you have modified your lights to use LEDs, you'll notice that the turn signals now blink very quickly. This is caused by the low resistance of the LEDs due to the fact that they use less energy. To correct the problem, you'll need to wire the turn signals in a parallel circuit. To do this, you'll be installing a resistor.
這裏說的解決辦法就是在新燈口處並聯焊一個適當的電阻（在這建議，阻值參考該種鎢絲燈泡內阻，取比其大幾倍，如5倍10倍，可行的話盡量往大選），但是轉向燈是雙燈絲結構（應該一個燈絲是轉向亮，另一個是刹車亮吧），你要分清電阻應並聯在轉向那個燈絲端子，分不清楚的話就兩麵各試一次。最懶辦法是任嘛甭管，任其快閃吧
Read more : http://www.ehow.com/how_5463302_fix-blink-led-turn-signals.html