Peugeot 206 Indicator flashes at double speed whilst back one doesn't work?

The indicator flasher units are designed to operate two 21w bulbs, 2 5w wing light bulbs and the pilot in your dashboard. If one of the bulb does not work, the flasher will make all lights blink at the reduced intervals then normal. Eventually causing rest of the bulbs to blow quickly or sometimes the flasher itself gives up. Replace the fused bulb or mend the cause of that light not working and they will all flash as normal.

Baz
January 2010