There are two wired chip plugs on the AS350 if you're flying the Arriel version. One on the pressure side, one on the scavenge.
There are also two chip plugs on the gearboxes, one on the MO1, one on the MO2.
Check all 4 plugs to narrow down the source of the light. Carbon on the plug will not illuminate the chip light, only metallic pieces.
Run a piece of clear scotch tape on the plugs to extract whatever material is on the plugs in order to examine them.