What was found
DURING CLIMB THROUGH 12,000 CHECK FIRE DET WARNING LIGHT ILLUMINATED FOR JUST A FEW SECONDS. NO OTHER FIRE LIGHTS ILLUMINATED. WHEN GAZE SHIFTED TO FIRE PANEL THE BTL LOW LIGHT WAS ON AND EXTINGUISHED AND THEN SO DID THE CHECK FIRE DET LIGHT. REMOVED FROM SERVICE. RELAMPED BTL LOW LIGHT ON FIRE DETECTION PANEL AS PRECAUTION. LIGHT OPERATES NORMALLY. "CHECK FIRE DET" WARNING NOT ILLUMINATED "BTL LOW" NOT ILLUMINATED. PERFORMED OPS TEST OF NACELLE FIRE DETECTION SYSTEM IAW Q400 AMM 26-11-00-710-801. OPS TEST GOOD. AIRCRAFT RETURNED TO SERVICE.