I have an RV-8A - 370 hrs over 2 1/2 years - with an early 4500. Shunt ammeter hookup. A few months ago, ammeter quit between flights. Would very intermittently come back online with no action on my part - so I figured a wiring problem. Troubleshot the two wires from the shunt to the sensor connector plug - no discrepencies. Replaced shunt connectors - problem still persists. Finally ran two new wires with new female D-sub pins into the connector. problem persists - although the ammeter worked when I initially connected the plug, but overnight gremlins appeared and next day ammeter was inop.

How likely is it that the problem is inside the box?

I'm out of airspeed, altitude and ideas!