B737-400 HAS UNSAFE INDICATION WHEN LNDG GEAR EXTENDED.

Narrative

ON FINAL APCH; LNDG GEAR HANDLE WAS LOWERED WITH NO GEAR DOWN AND SAFE INDICATIONS. A GAR WAS INITIATED; GEAR HANDLE WAS RAISED BUT WOULD NOT COME ABOVE 'OFF.' CREW; PAX; ATC; COMPANY WAS NOTIFIED. ATC PLACED ACFT (B737- 400) IN AN EXTENDED/VECTORING HOLDING PATTERN WHILE THE FLC REFERRED TO THE ACFT MANUAL AND ABNORMAL CHKLISTS. PRIOR TO MANUAL EXTENSION OF GEAR; ALL CIRCUIT BREAKERS WERE CHKED WITH NONE TO BE FOUND POPPED. THE MANUAL GEAR EXTENSION PROC RESULTED IN NO SAFE INDICATIONS. VISUAL VERIFICATION OF 3-DOWN-AND-LOCKED WAS MADE THROUGH THE GEAR PORTS; BY AN ACFT VECTORED IN BY ATC; AND BY TWR (TWR HAD CHKED ON THE INITIAL GAR AND ON THE SUBSEQUENT FLY-BY REQUESTED BY THE LCL AUTH). AN APCH WAS MADE TO A SAFE LNDG; ON FINAL THE CIRCUIT BREAKERS WERE RECHKED AND THE LNDG GEAR AIR AND GND RELAY AND LIGHTS CIRCUIT BREAKER WAS POPPED. IT WAS RESET PROVIDING NORMAL INDICATIONS PRIOR TO LNDG. THE ACFT WAS PINNED BY MAINT AFTER LNDG AND TAXIED TO THE GATE. IT IS NOT KNOWN IF THE CIRCUIT BREAKER WAS POPPED THE WHOLE TIME OR POPPED AFTER THE INITIAL SEARCH; IT IS A DIFFICULT AREA TO SEE.