ILS LOC GIVES FALSE SIGNAL RESULTING IN ACFT TURNING INTO THE ARPT EARLY.

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ILS 36 LOC WAS OUT TO MAINT. WHEN IT WAS RETURNED TO SVC; A NOTAM WAS ISSUED (D10/010) RWY 36R LOC UNUSABLE BEYOND 20 DEGS FROM CTRLINE. AN LGT X 5 MI E OF LOC BEGAN A TURN BECAUSE HIS EQUIP INDICATED HE WAS JOINING LOC. AN LGT Y AND AN MLT Z BOTH RPTED INDICATIONS THEY WERE ON THE LOC. BOTH WERE 4 MI W. MAINT CHKED THE EQUIP; AND FOUND NO EXPLANATION. THEY SAID THE EQUIP WAS MONITORING NORMALLY. ALL 3 ACFT INVOLVED EITHER SAW THE FIELD; OR REALIZED THE PROBLEM BECAUSE IT CONFLICTED WITH CTLRS INSTRUCTIONS. ONE ACFT ALSO NOTED HIS RNAV EQUIP INDICATED HE WAS NOT ON LOC; BUT HE WAS RECEIVING IT; AND THOUGHT HE WAS ON IT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR STATES THAT THE PROBLEM IS INTERMITTENT AND STILL EXISTS. FACILITY MGMNT AWARE OF PROBLEM AND ALERTED AF. AF CANNOT FIND ANYTHING WRONG. NOTHING OUT TO CTLRS FROM FACILITY MGMNT TO USE CAUTION WHEN ISSUING ILS APCHS. IT APPEARS THAT THEY ARE TRYING TO GET THE ILS SYS UPGRADED TO CAT III; SO SOME MODIFICATION PROBABLY MADE TO EXISTING EQUIP. NO FLT CHK YET; BUT ONE IS DUE. FORTUNATELY; ALL BUT ONE ACFT WAS ON A VISUAL APCH; BUT USING THE ILS AS A BACKUP. AF CLAIMS THAT EQUIP MEETS REQUIREMENTS WHENEVER THEY CHK IT.