A B737-300 HAD L MAIN GEAR UNSAFE LIGHT ON AFTER TKOF. GEAR RECYCLED LIGHT REMAINED ON AND ACFT RETURNED. FAA QUESTIONS RECYCLING OF GEAR IN CONFLICT WITH THE QRH.

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AFTER TKOF; WE GOT A L MAIN GEAR RED LIGHT. FOLLOWED QRH WHICH CALLED FOR 'GEAR DOWN'...IF 3 GREEN CHKLIST COMPLETE. AFTER CONSIDERING CONDITION OF ACFT; HYD; LIGHT TEST; CIRCUIT BREAKERS CONDITIONS; AND ASKING FLT ATTENDANTS IF THEY HEARD ANYTHING UNUSUAL OR FELT ANYTHING UNUSUAL (THEY SAID NO; BOTH FORWARD AND AFT); I ELECTED TO RECYCLE THE LNDG GEAR (1 TIME). AGAIN; WE GOT THE SAME INDICATION. I THEN ELECTED TO RETURN TO IAH AND MADE AN UNEVENTFUL LNDG AND TAXI TO GATE. THE DAY AFTER THIS EVENT; I WAS NOTIFIED THAT THE FAA WANTED INFO ON WHY I RECYCLED LNDG GEAR IF QRH DOES NOT CALL FOR IT. OUR QRH DOES NOT SAY NOT TO RECYCLE IT EITHER. HOWEVER; AT THE TIME OF THE EVENT AFTER CONSIDERING OTHER POSSIBILITIES; I FELT THAT I WAS DEALING WITH AN INDICATION PROB; THEREFORE I CHOSE TO RECYCLE. OUR QRH DIRECTS US TO 'COMMUNICATE AND ESTABLISH A PLAN' AND LACKING ANY DIRECTIVE (QRH; FOM; AFM) NOT TO RECYCLE GEAR; I FEEL THAT I WAS WITHIN THE SPIRIT OF THE QRH AND MORE SPECIFICALLY THE FOM WHICH DIRECTS US TO USE 'COMMON SENSE AND GOOD JUDGEMENT.' AS I NORMALLY DO AFTER A MECHANICAL SIT WHICH DOES NOT YIELD AN IMMEDIATE ANSWER AS TO WHY IT OCCURRED; I FOLLOWED UP WITH MAINT CTL AND THEY INFORMED ME THAT IT WAS AN INDICATION PROB; THEY REPLACED THE UP-LOCK LANDING MECHANISM. IN CLOSING; I WOULD LIKE TO STRESS THAT IF I HAD ANY DOUBTS AS TO THE CONDITION OF THE LNDG GEAR; I CERTAINLY WOULD NOT RECYCLE IT AS I DID.