What was found
PILOT/OWNER REPORTED THAT RADIO INDICATOR BACKLIGHTING AND RADIO CONTROL BACKLIGHTING HAD NOT WORKED SINCE AIRCRAFT DELIVERY. TROUBLESHOT SYSTEM, FOUND THAT PIN 1 OF JC005 WAS AT GROUND POTENTIAL, PREVENTING DIMMER POTENTIOMETER FROM FUNCTIONING AS IT IS SUPPOSED TO. REMOVED WIRE 6JC015-1JC005 FROM CIRCUIT AND FOUND THAT RADIO LIGHTING WORKED AS IT WAS SUPPOSED TO. WIRE 6JC015-1JC005 HOOKS INTO THE WARNING/CAUTION ANNUNCIATOR. THIS ANNUNCIATOR HAS ITS OWN SWITCH/ LOCATED AT THE TOP OF THE RADIO STACK/ FOR BRIGHT/DIM/TEST.