2000 Dodge Dakota left turn signal/brake light

My 2000 Dodge Dakota is having a problem with left turn signal/brake light, on dash left turn signal blinks fast so I thought a bulb was out. I replaced all the bulb in front an back on left side but it still does it. The brake light doesn't work either the sockets an wiring seem fine. it you start to put on left turn signal at times you can hear a buzzing noise from fuse panel area does this mean my flasher unit is at fault if not what else should I look at? Thanks.