C8 is indicates a current sensing failure, which usually indicates a fault within the controller, which is by now is unlikely for a replacement to be sourced. However its well worth looking at the current sensing leads attached to the current sensing shunt mounted on the front of the main rectifier, (it looks a bit like an oversized razor blade). Also have a look at all the bolted shunt mountings, any signs of loose connections and / or over-heating ? If so file clean and, or replace.