What was found
UNCOMMANDED DISCHARGE OF ENG IGNITERS DURING ROUTINE 100 HR MX WHILE PERFORMING FUNCTION CHECK OF PROBES ELEMENTS, AN UNCOMMANDED DISCHARGE OF THE IGNITERS OCCURRED. GROUND POWER WAS APPLIED AND ON, PROBES SWITCH TURNED ON AT PANEL FOR APPX 30 SECS. BY PILOT IN COCKPIT WHILE MX CONDUCTED A WALK AROUND TO VERIFY PROBES ELEMENT HEAT.ONFINAL STAGE OF CHECK AT OR BEYOND TIME PROBES SWITCH SET TO OFF A D DISSIPATING DISCHARGE SOUND WAS HEARD FROM/AROUND THE ENG (APPX 5-6 FLASHES)THEN STOPPED. THE ENG WAS COMPLETELY DE-COWLED. ENGINE MX PERFORMED EARLIER IN THE DAY, COMPLETE WITH A FUNCTION CHECK OF THE IGNITERS. THEY WERE SECURELY INSTALLED AT THE TIME OF THE INCIDENT. THIS ANOMALY HAS OCCURRED 3 TIMES PREVIOUSLY.