What was found
(CAN) DOOR WARNINGS: 6000 FEET IN DESCENT, DOOR WARNING FOR RT AFT SERVICE DOOR, AT SAME TIME HAD LIGHT TO MODERATE TURBULENCE. WARNING DISAPPEARED JUST BEFORE LDG. UPON ARRIAL, DOOR SENSOR LUBRICATED & RIGGING OF DOOR CHECKED W/O REMARKS. SAME PROBLEM APPEARED ON PREVIOUS DAY WITH EXACT SAME SYMPTOMS & DURING SAME STAGE OF FLT. SIX DAYS LATER, PROBLEM REAPPEARED & AGAIN ON 7TH DAY AFTER REPORTED INCIDENT DURING LAST 2 INCIDENTS, ICE REPORTED ON DOOR SENSOR & ADJUSTMENT PERFORMED, DUE TO SENSOR INDICATING FAR. SENSOR CLEANED, LUBRICATED&ADJUSTED. AFTER THAT, DOOR DID NOT GET WARNING UNTIL 19 FEB 2002, WHERE ICE AGAIN REMOVED FROM SENSOR.