i am having electrical faults with my c8 rev counter and the speedo go off?

ignition light came on i drove a few mile then my stop light and abs light came on, engine came to a stand still with stop light and traction control light coming on battery had gone flat i foud out i needed a new altinator i fitted a new altinater but now rev counter and speedo gos off stop light comes on and traction control light comes on for a few seconds then goes off again can you help because i have had an electrician out who cant find the fault with his diagonostic machine.