A MAINTENANCE SUPERVISOR AND MECHANIC DESCRIBE WHY THEY BELIEVED THAT A CATEGORY-3 RECERTIFICATION WAS NOT REQUIRED FOR AN 'HGS FAULT LIGHT ILLUMINATED IN FLIGHT' CONDITION ON A B737-700.

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MECH CAME TO ME WITH HIS LOGBOOK CONTAINING THE DISCREPANCY; 'HEADS UP GUIDANCE SYS FAULT LIGHT ILLUMINATED INFLT.' HE TOLD ME THAT WHEN HE PWRED UP THE ACFT; THE FAULT LIGHT DID NOT ILLUMINATE. HE PERFORMED THE OPS TEST PER CMM WITH NO FAULTS DETECTED OR NOTED. HE ASKED ME IF A CAT III UPGRADE WAS REQUIRED. I SAID NO; BECAUSE OF THE FOLLOWING REASONS: 1) IT WAS A TERMINATING FLT; NOT A THROUGH-FLT. 2) ACFT WAS NEVER DOWNGRADED. 3) NO HEADS UP GUIDANCE SYSTEM COMPONENTS WERE DISTURBED. 4) NO 30 DAY HISTORY OF HEADS UP GUIDANCE SYSTEM PROBS (NO 90 DAY AND NONE TO DATE). 5) ALL WE DID WAS A TEST; NO EQUIP USED. SINCE WE DIDN'T ACTUALLY FIND A FAULT AND WE DIDN'T DO ANYTHING BUT PUSH A BUTTON; I FELT AN UPGRADE OR RECERTIFICATION WAS NOT ABSOLUTELY REQUIRED. SYSTEM CAPABILITIES AND ACFT FLT ABILITIES NEVER COMPROMISED. TOO MANY CONFLICTING REFERENCES IN THE PROCS MANUAL. IT ALL NEEDS TO BE BROUGHT TOGETHER IN ONE; SIMPLE TO UNDERSTAND LOCATION. SUPPLEMENTAL INFO FROM ACN 809035: THERE WAS A PLT WRITE-UP IN THE LOGBOOK -- STATED THAT HEADS UP GUIDANCE SYSTEM FAULT LIGHT CAME ON DURING FLT. WHEN I PWRED THE ACFT UP; FAULT LIGHT WAS NO LONGER THERE. I RAN TEST AND FOUND NO FAULT TO SYSTEM. I RPTED PROB TO SUPVR AND ASKED IF ACFT NEEDED TO BE RECERTIFIED BACK TO CAT III STATUS. THE ANSWER WAS NO.