A TECHNICIAN RPTS CARRIER HAS 3 CVR SYS FOR THE B737-300 WITH PARTS NOT INTERCHANGEABLE AND WITH LIMITED ACCURATE EFFECTIVITY INFO.

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MAINT MANUAL SUPPLEMENT TO 23-71-00 PAGE 1 STATES THAT THERE ARE 2 CVR SYS INSTALLED; AND ARE INTERCHANGEABLE. THERE IS NOW 3 SYS; AND ARE NOT READILY INTERCHANGEABLE. THE MAINT MANUAL DOES NOT ADDRESS THE 3 CVR TYPE. INSTEAD; WE ARE TO USE LCL COMPUTER SYS TO VERIFY PART NUMBER. ORIGINAL CONFIGN WAS COMPANY PART NUMBER COCKPIT UNIT 32319 AND CVR 92309. THE 92309 UNIT WAS FAULTY. PART SENT TO REPAIR THE ACFT WAS A 2320. THERE IS NO MAINT MANUAL REF TO THIS UNIT. MAINT CTL WAS CONTACTED FOR A RESOLUTION. ABOUT 3 HRS LATER; THEY INFORMED ME THAT COCKPIT UNIT 32319 AND CVR 2320 WERE A COMPATIBLE COMBINATION PER COMPUTER SYS. MAINT CTL SAID TO 'INSTALL THE UNIT AND PRESS TO TEST; IT EITHER WORKS OR IT DOESN'T.' DAYS LATER I WAS INFORMED THE CVR FAILED TO TEST RESOLUTION WAS A PARTS CONFIGN WAS FOUND TO BE INCOMPATIBLE. CORRECTION WAS TO CHANGE THE COCKPIT UNIT TO CONFIGURE IT TO THE CVR. LATER RESEARCH INTO COMPUTER SYS REVEALS THAT COCKPIT UNIT 32319 CONFIGURES TO 2320 CVR; BUT IF USING 2320 CVR TO CONFIGURE; IT STATES TO USE A 32313 COCKPIT UNIT.