A B737 FLIGHT CREW NOTICED WARNING FLASHES OF THE MASTER CAUTION FIRE WARNING AND THEN A STEADY ILLUMINATION AND WARNING HORN AT ROTATION.

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JUST AT ROTATION; WITH THE NOSEWHEEL LIFTING; THERE WAS A MOMENTARY COUPLE FLASHES OF THE MASTER CAUTION FIRE WARNING SYS ON THE GLARE SHIELD. BY THE TIME I COULD LOOK AT THE FIRE CTL PANEL; THE INDICATION HAD EXTINGUISHED. I ASKED OUR SYS TECH OCCUPYING THE JUMPSEAT TO KEEP AN EYE ON THE PANEL AND CONTINUED THE CLB NOT KNOWING IF IT WAS AN ENG; APU OR WHEEL WELL WARNING. PASSING 800 FT; AS THE GEAR CAME ALL THE WAY UP; 2 MORE FLASHES OCCURRED AND IT WAS DETERMINED THAT IT WAS THE WHEEL WELL FIRE WARNING SYS. ATC WAS VERY BUSY AT THIS TIME. MY INITIAL PLAN WAS TO ASK FOR VECTORS BACK AROUND FOR A LNDG AND HAVE MAINT INVESTIGATE THE ISSUE. BY THE TIME I COULD DO THIS; WE WERE PASSING 4000 FT ON OUR WAY TO 5000 FT ON A RADAR VECTOR FOR THE DEP. AT THIS TIME; THE WHEEL WELL FIRE WARNING ILLUMINATED STEADY AND THE APPROPRIATE HORN SOUNDED. THE HORN WAS CANCELLED AND THE APPROPRIATE CHKLIST PERFORMED. IMMEDIATELY UPON SELECTING THE GEAR TO THE DOWN POS (THE ONE ACTION ITEM ON THE CHKLIST) THE WARNING EXTINGUISHED. AFTER DISCUSSION AMONG THE CREW; I ELECTED NOT TO DECLARE AN EMER. I ASKED FOR RADAR VECTORS BACK TO THE FIELD FOR AN APCH; NOTIFIED OUR COMPANY DISPATCH AND FIRE DEPT OF THE SITUATION AND BRIEFED THE OTHER 6 PAX ON BOARD OF THE SITUATION AND POSSIBLE LNDG COMPLICATIONS. A NORMAL LNDG WAS PERFORMED USING MINIMAL BRAKING TO MINIMIZE ANY ADDITIONAL HEAT GENERATION IN THE BRAKES. AFTER CLRING THE RWY; WE HAD OUR COMPANY FIRE TRUCKS PERFORM A VISUAL INSPECTION ON THE GEAR PRIOR TO TAXIING BACK INTO THE RAMP FOR MAINT. NO VISIBLE EVIDENCE WAS FOUND. UPON TROUBLESHOOTING; IT WAS DISCOVERED THAT THE CENTER GROUND FOR THE WHEEL WELL FIRE LOOP HAD HIGHER THAN NORMAL IMPEDANCE AND THAT WHEN VIBRATED; IT WOULD PROVIDE AN 'OPEN' CAUSING THE MOMENTARY WARNING. THE FIRE LOOP WAS REPLACED; GND TESTS COMPLETED AND THE ACFT RETURNED TO SVC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT ONLY THE MAIN LEFT AND RIGHT WHEEL WELLS HAVE FIRE WARNING USING TWO SEPARATE LOOP ELEMENTS. THE FIRE WARNING LIGHTS THAT COME ON ONLY SHOW WHEEL WELL; NOT LEFT OR RIGHT WHEEL WELL. THE MAIN GEARS ARE OF HEAVIER WEIGHT CARRYING DESIGN. HE HASN'T HEARD OF ANY OTHER REPORTS OF A SIMILAR FIRE WARNING FAULT ISSUE WITH THIS MODEL TYPE ACFT.