Narrative:

I was cruising at FL180 heading wsw circumnaving thunderstorms en route to ZZZ1 to clear customs. Approximately 60 NM from ZZZ1; I had the left engine fire annunciator illuminate and left engine fire extinguish button illuminate. I immediately had my copilot retrieve the emergency checklist and stand by. The left engine gauges suggested everything ok. No smoke was observed. I declared an emergency and after 2 mins was satisfied nothing was wrong and landed at the nearest airport (ZZZ) and deplaned my passenger immediately and led them into the FBO. Customs did not like that; but I did that in the interest of safety. An inspection revealed faulty fire detection sensors due to being waterlogged (heavy rain). I rescinded the declaration of emergency 15 mi from ZZZ.

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Original NASA ASRS Text

Title: A BEECH KINGAIR 100 FLT CREW GOT AN ENG FIRE WARNING. THEY DECLARED AN EMER AND DIVERTED TO ZZZ.

Narrative: I WAS CRUISING AT FL180 HDG WSW CIRCUMNAVING TSTMS ENRTE TO ZZZ1 TO CLEAR CUSTOMS. APPROX 60 NM FROM ZZZ1; I HAD THE L ENG FIRE ANNUNCIATOR ILLUMINATE AND L ENG FIRE EXTINGUISH BUTTON ILLUMINATE. I IMMEDIATELY HAD MY COPLT RETRIEVE THE EMER CHKLIST AND STAND BY. THE L ENG GAUGES SUGGESTED EVERYTHING OK. NO SMOKE WAS OBSERVED. I DECLARED AN EMER AND AFTER 2 MINS WAS SATISFIED NOTHING WAS WRONG AND LANDED AT THE NEAREST ARPT (ZZZ) AND DEPLANED MY PAX IMMEDIATELY AND LED THEM INTO THE FBO. CUSTOMS DID NOT LIKE THAT; BUT I DID THAT IN THE INTEREST OF SAFETY. AN INSPECTION REVEALED FAULTY FIRE DETECTION SENSORS DUE TO BEING WATERLOGGED (HVY RAIN). I RESCINDED THE DECLARATION OF EMER 15 MI FROM ZZZ.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.