What was found
AT 300FT ON FINAL, GOT GPWS WARNING (TOO LOW GEAR, PULL UP). NOSE GEAR INDICATOR WENT BLANK. DID EMERG PROCEDURES INCLUDING PULLING GPWS AND HORN C/BS. DID LOW FLY BY TOWER TO CONFIRM GEAR DOWN. ON WAVEOFF DID AGRESSIVE PULLUP. NOSEGEAR INDICATOR WENT BLANK TO GREEN. ALL SECONDARY INDICATORS (PIN AND AUX MAIN INDICATORS) INDICATED DOWN THROUGHOUT. TROUBLESHOT SYSTEM. SUSPECT MOISTURE IN THE LEG LOCK MICROSWITCH OR CHANGEOVER SWITCH. REPLACED BOTH SWITCHES I.A.W. HS 125-800XP MM RIGGED SWITCHES & SAFETIED GEAR OPS CK SATISFACTORYREF CH 32-60-00 PG 502 PG 504.