During phase 1 I had a few of the vans gauges intermittently go off line. In the end, I took a closer look at the terminal crimps, grounding points, and tightness of the connections on the back side of the vans instruments. For the past 250 hrs, I haven't had any issues. Wiggle the wires and see if the tach gauge comes back on line.
As a side note, while flying, an audible whine would intermittently be heard. The frequency of the whine would change with rpm. I had a lot of concern as to where this noise was coming from. Answer: I removed the short tach cable and it was dry (no lube) on the inside. I added lithium grease and all is well.
Jim Diehl 7A