A FOKKER 100 WHILE TAXIING FOR TKOF RETURNS TO THE GATE DUE TO AFT CAB RPT OF TICKING IN AFT LAV. CAUSED BY HIGH TENSION IGNITION LEAD ARCING.

Narrative

WHILE DOING MY FINAL LAVATORY CHK BEFORE TAKING MY JUMPSEAT. I HEARD A UNUSUAL TICKING NOISE FROM THE AFT LAV; ACFT LEFT. I IMMEDIATELY CHK THE TOILET TO SEE IF THE FLAP INSIDE WAS MOVING; IT WAS NOT SO I CALLED FA #1 ADVISED HER TO TELL THE CAPT THAT THERE WAS AN UNUSUAL TICKING NOISE IN THE LAV ACFT LEFT. I THEN ASKED A NON-REV CREW MEMBER TO COME TO THE BACK TO SEE IF SHE COULD IDENT THE NOISE. BY THIS TIME THE TICKING SOUND HAD GOTTEN LOUDER. I THEN INFORMED THE CAPT THAT THE SOUND WAS COMING FROM BEHIND THE PAPER SUPPLY PANEL. I PULLED THE SUPPLIES OUT AND NOTICED A BLUE SPARK WITH EACH TICK. THE CAPT RETURNED TO THE GATE AND CALLED MAINT. I WAS INFORMED THAT THE PROB WAS A MALFUNCTION WITH THE IGNITOR CTL BOX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED DURING TAXI FOR TKOF SHE HEARD WHAT APPEARED TO BE A LOUD TICKING IN THE AFT LEFT LAV. THE RPTR SAID SHE WENT INTO THE LAVATORY AND LOCATED THE TICKING FROM BEHIND THE TOWEL AND PAPER SUPPLY COMPARTMENT. THE RPTR STATED WHEN OPENING THE COMPARTMENT AND LOOKING AFT SHE OBSERVED BLUE FLASHES OR SPARKS. THE RPTR SAID THE FIRST FA WAS ADVISED TO ALERT THE CAPT AND RETURN TO THE GATE. THE RPTR SAID MAINT FOUND THE IGNITOR UNIT LOCATED AFT OF THE TOWEL AND PAPER COMPARTMENT DEFECTIVE AND WAS REPLACED.