C310 PLT ON A VECTOR TO IND FOR A VISUAL APCH FOLLOWS THE WRONG ACFT AND HAS A CLOSE ENCOUNTER WITH THE DC9 HE WAS TO FOLLOW.

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I WAS APCHING THE IND ARPT FROM THE N AND RECEIVED A VECTOR OF 180 DEGS AROUND THE W OF THE ARPT FOR THE ILS FOR RWY 5L. I WAS LEVEL AT 3000 FT MSL W OF THE ARPT WHEN I RECEIVED THE INSTRUCTION TO TURN L TO 140 DEGS AND DSND TO 2500 FT MSL AND THAT I HAD TFC AHEAD. THIS WAS AN EFFORT BY THE CTLR TO GET ME NEAR THE ARPT IN THE HOPES THAT I COULD COMPLETE THE VISUAL APCH TO RWY 5L. WE HAD SPOKEN ABOUT TRYING TO ACCOMPLISH THIS; AS ANOTHER ACFT DID THE SAME THING EARLIER. IN MY REPLY TO THE CTLR; I ACKNOWLEDGED THE HDG AND ALT; AND IN ADDITION THAT I HAD TFC AT MY 10 O'CLOCK POS AND A LITTLE BELOW MY ALT AND THAT 'I DIDN'T THINK IT WAS MY GUY.' THE CTLR RESPONDED THAT IT WAS MY TFC TO THE L AT 2300 FT MSL; AND FOLLOW HIM FOR RWY 5L. I TURNED TOWARDS THE TFC TO FOLLOW HIM ON FINAL AND APPROX 1 MIN LATER THE CTLR SWITCHED ME TO TWR ON 120.9. I CALLED TWR AND TOLD THEM THAT I WAS WITH THEM; #2 FOR RWY 5L. THE CTLR EXCLAIMED THAT I WAS SUPPOSED TO BE ON 121.1 AND ON A HDG OF 140 DEGS AND 2500 FT (WHICH I WAS AT 2500 FT; BUT NOT ON HDG SINCE I WAS FOLLOWING WHAT I WAS TOLD WAS MY TFC!). MOMENTS LATER; WHILE I WAS TURNING BACK TO 140 DEGS; HOLDING 2500 FT MSL AND TUNING 121.1; I NOTICED LNDG LIGHTS COMING OUT OF 'THE MURK' NOT TOO FAR FROM MYSELF AND SLIGHTLY HIGHER TO THE R. I IMMEDIATELY TURNED R TO ABOUT 260 DEGS AND CALLED ON 121.1. THAT CTLR EXCLAIMED I WAS ON THE WRONG FREQ AND HDG. I SWITCHED TO THAT FREQ; WHICH WAS THE ORIGINAL CTLR I HAD W OF THE ARPT; AND HE CALMLY; HELPFULLY AND QUICKLY EXPLAINED THAT I HAD FOLLOWED THE WRONG ACFT (APPARENTLY THE TFC THAT I TURNED TO AVOID WAS THE DC9 I WAS SUPPOSED TO FOLLOW). HE THEN ASKED IF I STILL HAD THE ARPT IN SIGHT AND CLRED ME FOR THE VISUAL FOR RWY 5R. (I WAS NOW THROUGH THE FINAL APCH COURSE FOR RWY 5L BECAUSE AFTER I TURNED TO AVOID TFC; I TURNED BACK TO 140 DEGS AFTER IT PASSED. I THINK THAT THERE WERE SEVERAL OTHER FACTORS THAT MAY HAVE CONTRIBUTED TO THIS OCCURRENCE. THE FIRST WAS THAT WHILE INBOUND; I WAS INFORMED THAT THE MODE C PORTION OF MY XPONDER SYS WAS INDICATING INCORRECTLY. I ASSUME THAT THE INBOUND TFC I AVOIDED ON THE APCH TO RWY 5L HAD TCASII AND I AM NOT SURE WHETHER HE MAY HAVE BEEN ALERTED WITH THE MODE C PORTION OF MY SYS TURNED OFF AS I WAS REQUESTED TO DO SO BY ATC. ANOTHER FACTOR MAY HAVE BEEN THE WX. IT WAS MARGINAL AT THE TIME AND I THINK THAT A MORE POSITIVE TFC IDENT MAY HAVE BEEN MADE IF BETTER CONDITIONS WERE PRESENT AT THE TIME. THE LAST MAY HAVE BEEN CTLR AND PLT WORKLOAD. THE FREQS WERE SOMEWHAT BUSY; AND I WAS ALSO BUSY AS A SINGLE PLT WORKING TO CONFIGURE FOR A QUICK DSCNT AND TURN INBOUND.