Ford Repair: Electrical problems, turn signal switch, lighting problem

Question
I got two questions. The first one is what does the button O/D do on a 1996 Ford Mustang when its on or off?


Also there is a problem with the lef side of my cars electrical system? For some reason the brake and signal light wont turn on but the lightbulbs are still good? and the turn signals blink faster when your turning left than right. And lastly the left speakers dont work? I know i should get it checked out but i want to know wats wrong. I've checked the fuses but all of those are good?

Answer
OD=overdrive. When the light is ON, the overdrive is OFF, when the light is OFF, the overdrive is on.

Your lighting problem is most likely the turn signal switch in the steering column.

As far as the speakers, that could be a connector, the speaker, or the radio.