FLC OF ACR MLG ACFT DEVIATED FROM ASSIGNED HDG IN RESPONSE TO A TCASII RA DURING A SID CLBOUT.

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PRADO 2 DEP FROM ONT; L TURN DIRECT PDZ. ASSIGNED ALT 7000 FT. INITIAL CONTACT WITH ONT DEP; CTLR ISSUED NEW ALT ASSIGNMENT OF 3000 FT AS WERE CLBING THROUGH 2700 FT; AND CALLED TFC AT 12 O'CLOCK; 4000 FT; THAT HE 'WASN'T TALKING TO.' SIMULTANEOUSLY; TCASII ANNUNCIATED RA 12 O'CLOCK WITHIN 5 MI WITH NO PREVIOUS TA; THEN FAILED AND WENT BLANK; ANNUNCIATING NO TCASII. WHILE CONTINUING SID TURN DIRECT PDZ WE OBSERVED TFC AT 12 O'CLOCK AND CONTINUED L TURN APPROX 30 DEG FURTHER TO AVOID TFC. RECYCLED TCASII TO TA SEVERAL TIMES TO REINSTATE. UNABLE TO ADVISE ATC OF DEV AS FREQ VERY CONGESTED. CTLR STILL TRYING TO CONTACT THE INITIAL CALLED ACFT AT 12 O'CLOCK. WHILE INITIATING TURN BACK TOWARDS PDZ; ATC ASSIGNED HDG 180 DEG AND 4200 FT; THEN 7000 FT. WHILE CLBING THROUGH 6500 FT RECEIVED ANOTHER TCASII RA WITH DSCNT ANNUNCIATED. WE FOLLOWED RA COMMANDS WHEN CTLR ASKED WHY WE MADE WIDE L TURN. I ASKED HIM TO STANDBY. AFTER WE HAD RESOLVED RA; I EXPLAINED WE JUST HAD RA WITH PREVIOUS RA EARLIER; AND APOLOGIZED FOR DEV. SUPVR REQUESTED WE CALL ONT TRACON UPON LNDG; WHICH I DID. SITUATION APPEARED RESOLVED WITH BOTH OF US AGREEING AN EARLIER CALL TO ATC WOULD HAVE BEEN HELPFUL. CONTRIBUTING FACTORS WERE IMMEDIATE LEVEL OFF; CTLR CALLED TFC AT 12 O'CLOCK WITH NO CONTACT; TCASII WARNING AND SUBSEQUENT FAILURE; AND CONGESTED FREQ. SUPVR STATED PROBLEM WAS TURNING TOWARD ONT APCH TFC; BUT SINCE WE WERE ALREADY IN L TURN; R TURN SEEMED UNADVISABLE. NO CONFLICT WAS RPTED.