MODE C FAILURE DISCOVERED AFTER DEP. REQUESTED WAIVER FOR RETURN TRIP.

Narrative

THIS FLT FROM SANTA ANA TO MONTGOMERY FIELD. TKOF WAS NORMAL. DURING CLBOUT; COAST DEP ASKED OUR ALT; WHICH WAS GIVEN. WE WERE INFORMED THAT OUR MODE C WAS OFF BY SEVERAL THOUSAND FT; AND ASKED TO RECYCLE; WHICH DID NOT IMPROVE OR CORRECT THE ALT SQUAWK. COAST ASKED US TO STOP THE MODE C AND CONTINUE. I ASKED COAST WELL OUTSIDE THE 30 NM MODE C VEIL IF THEY COULD WORK A HDOF; AND WAS TOLD THEY WERE IN THE PROCESS OF DOING SO. I ASSUMED THAT COAST HAD INFORMED SAN DIEGO APCH THAT WE HAD AN INOP MODE C AND WAS SURPRISED WHEN; AFTER PASSING OCEANSIDE VOR; WELL INSIDE THE 30 NM VEIL; I WAS ASKED TO SQUAWK 1200; FREQ CHANGE APPROVED. SAN DIEGO GAVE US A SQUAWK CODE AND HAD NO IDEA THAT OUR MODE C WAS IN ERROR. THE CTLR CLRED US THROUGH AND ADMONISHED ME TO 'GET THAT THING FIXED' BEFORE LEAVING. SINCE WE NEEDED TO RETURN THAT NIGHT; AND NO REPAIR FACILITY WAS OPEN; AND THE OWNER OF THE AIRPLANE (IT WAS RENTED) WANTED US TO BRING IT TO HOME BASE (SNA) FOR REPAIRS; WE CALLED SAN DIEGO AND GOT A MODE C WAIVER AND RETURNED WITHOUT FURTHER PROBLEM. I FEEL FIRST THAT PLTS NEED TO BE AWARE THAT ATC MAY OR MAY NOT INFORM EACH CTLR IN SUCCESSION OF AN EQUIP FAILURE. IN OUR CASE; WE WOULD HAVE TURNED AROUND HAD I THOUGHT THAT SAN DIEGO DIDN'T KNOW ABOUT OUR MALFUNCTIONING MODE C. SECOND; BEING AWARE OF THIS; PLTS NEED TO ASK WHAT THE CTLR IS DOING WHEN SOMETHING ISN'T FIRMLY ESTABLISHED. I AM AWARE OF THE IMPORTANCE OF MODE C IN HELPING CTLRS KEEP EVERYONE APART AND HAD NO INTENTION OF CAUSING A PROBLEM. I DID LEARN HOW TOUGH IT IS WHEN A CTLR MUST ASK FOR YOUR ALT BEFORE HE CAN ISSUE INSTRUCTIONS TO OTHER ACFT. FINALLY; I WONDER IF THERE IS ANY WAY TO VERIFY TRANSPONDER OP ON THE GND. IN THIS CASE; THE TRANSPONDER TEST SETTING INDICATED NORMAL OP EVEN AS I WAS TOLD IT WASN'T FUNCTIONING AND GAVE THE SAME INDICATIONS ON THE GND BEFORE THE RETURN FLT. THIS WAS EXTREMELY FRUSTRATING! IN FACT; ON BEING CLRED INTO SAN DIEGO'S TCA; I WAS TOLD THAT OUR MODE C WAS AGREEING WITH OUR ALTIMETER; THEN TOLD MOMENTS LATER THAT IT WASN'T; THEN IT WAS; ETC. ONLY THE CTLR CAN MONITOR THIS.