Larry, I recently had the same problem on one of our 740s. Remove the instrument cluster (two screws). Remove and clean all connections. I use a "pink pearl" eraser (as on a pencil)and carefully used it on all the ribbon trace connection points and pay special attention to the grounds. The one under the white plastic cap (below the tach)was the main culprit for me. Hope this helps! As a computer technician (for 15 years) I used pink pearl erasers for cleaning edge connectors on adaper boards. It's just abrasive enough to remove oxidation without removing plating.

Check the grounds. Replace the flasher.