BE20 CPR FLC NOTE A FIRE WARNING ON #2 ENG WHILE IN IMC FLT. AFTER DECIDING AGAINST AN INFLT DIVERSION TO ALTERNATE ACCOUNT ENRTE WX; THEY ELECT TO CONTINUE TO DEST; TEB ARPT.

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AFTER A NORMAL PREFLT AND DEP WE WERE ASSIGNED 6000 FT AS A FINAL. THE WX WAS A MIX OF MODERATE RAIN AND SNOW; TEMP WAS HOLDING ABOUT +1 DEG C; SO THE WATCH FOR ICE CONDITIONS WAS BEING PAID STRICT ATTN. AFTER 15-20 MINS IN CRUISE; THE R ENG FIRE WARNING LIGHT ILLUMINATED AND AS IT DOES NORMALLY; ACTIVATED THE MASTER WARNING LIGHTS ON THE PLT/COPLT GLARESHIELDS. BOTH PLTS IMMEDIATELY LOOKED AT THE R ENG TO SEE IF THERE WAS ANY EVIDENCE OF FIRE. I SAW NONE; BUT ASKED THE FO TO CONTINUE TO WATCH IT SINCE HE HAD A MUCH BETTER VIEW. I BEGAN SCANNING ENG INSTS TO LOOK FOR ANY ABNORMALITIES. NO ABNORMALITIES WERE FOUND AND NEITHER ENG SHOWED SIGNS OF FIRE; SO THE DECISION WAS MADE TO LEAVE THE ENG RUNNING UNLESS SOMETHING INDICATED A NEED FOR SHUTDOWN. AT THIS TIME; BECAUSE THE PROB WAS UNCLR; THE CREW DISCUSSED OPTIONS FOR THE REMAINDER OF THE FLT. OUR ORIGINAL DEST WAS 15 MINS FLT TIME; 2 OTHER ARPTS HPN AND DXR WERE UNDER 10 MINS FLT TIME. I ADVISED ATC WE WISHED TO DIVERT TO HPN AND I ADVISED THEM OF THE PROB. I DID NOT THEN OR AT ANY TIME DECLARE AN EMER. APCH GAVE ME THE WX AT HPN AND BECAUSE OF THE SIT; I DISCUSSED THE WX WITH THE FO AND THEN ADVISED ATC WE WOULD THEN LIKE TO CONTINUE TO OUR ORIGINAL DEST (TEB). WX WAS 300 FT 1 MI VISIBILITY AT HPN; JUST AT MINIMUMS; 900 FT 4 MI AT TEB; WELL ABOVE MINIMUMS. THE CTLR OFFERED DXR; WHICH WAS 700 FT 2 MI VISIBILITY; I ADVISED THAT DUE TO TERRAIN AND WX WE WOULD CONTINUE TO TEB. THE NEED TO DEAL WITH ONLY 1 PROB; THE FIRE LIGHT; AND NOT THE WX AND TERRAIN; MADE TEB SEEM LIKE A BETTER OPTION. ALL INDICATIONS REMAINED NORMAL THROUGHOUT THE APCH. WE DID REQUEST NO DELAY INTO TEB AND ALSO ASKED FOR CFR JUST IN CASE SOMETHING OCCURRED ON THE LNDG. THE ACFT WAS LANDED WITHOUT INCIDENT AND NO FIRE OCCURRED. INVESTIGATION INTO THE PROB REVEALED VERY LITTLE AS TO WHAT THE CAUSE FOR THE FAULT MAY HAVE BEEN. NO EVIDENCE OF FIRE WAS FOUND AND ALL SYS TESTED NORMALLY. I CAUTION KING AIR PLTS WHO ARE INCLINED TO MINIMIZE FIRE WARNING LIGHTS BECAUSE THE SUN OR THE PRECIP SETS THEM OFF ON OCCASION. THIS WAS A SERIOUS SYS MALFUNCTION THAT MAY HAVE DISABLED THE SYS IF LEFT TO GO LONG ENOUGH. AS FAR AS THE PRIORITY HANDLING AND FIRE TRUCKS; BETTER SAFE THAN SORRY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THIS ACFT HAS A KNOWN EQUIP DESIGN PROB IN THE FIRE WARNING SYS. THE SUN OR RAIN CAN SET THIS ALARM SYS OFF. THE ACFT CHKLIST SAYS TO CHANGE ACFT'S HDG IF EXPOSED TO THE SUN SO AS TO ADJUST THE REFLECTIVE LIGHTING EFFECT. BECAUSE OF THIS CHKLIST RPTR SAYS THE MANUFACTURER MUST KNOW OF THE PROB. IN ADDITION; THERE ARE KING AIRS THAT HAVE HAD A MODIFIED CONTINUOUS LOOP SENSOR SYS INSTALLED WHERE THE ALARM IS SET OFF ONLY WHEN THE CURRENT IS BROKEN. THIS ACFT DID NOT HAVE THAT NEW SYS. HE FURTHER STATED THAT THERE ARE THOUSANDS (?) OF KING AIRS OUT THERE; WITH OR WITHOUT THE NEW SYS. THERE HAD BEEN ONE AIRWORTHINESS DIRECTIVE PUT OUT FOR AN INFRARED SENSOR CHANGE BUT HE DIDN'T THINK IT WAS ON THE 200 SERIES KING AIR.