What was found
DURING CLIMB THROUGH 15,000 FEET, AFT SERVICE DOOR WARNING LIGHT ILLUMINATED IN FLIGHT. LEVELED OFF AT 15,000' AND RAN EAC CHECKLIST. PRESSURIZATION NORMAL, LIGHT CONTINUED TO ILLUMINATE AND GO OFF AGAIN. DID THIS FOR 15 MIN. RETURNED TO FIELD, LANDING UNEVENTFUL. LIGHT REMAINED OFF THE REST OF THE FLIGHT. PERFORMED GVI OF AFT SERVICE DOOR CLOSED AND LOCKED SENSORS AND WIRING. FOUND NO DEFECTS. PRESSURIZED AIRCRAFT, NO ABNORMAL DOOR INDICATIONS NOTED. INTERROGATED PSEU, FOUND NO RELATED FAULTS. FOUND ASDRCL SENSOR OUT OF RIGGING GAP TOLERANCE. ADJUSTED ASDRCL PROX SENSOR IAW Q400 AMM 52-71-01-830-808. INDUCTANCE VALUE WITHIN LIMITS PER Q400 AMM 32-61-00-280-801. PERFORMED OPERATIONAL CHECK OF AFT SERVICE DOOR IAW Q400 AMM TASK 52-41-00-710-801. OPERATIONAL CHECK GOOD. NO PARTS REPLACED.