What was found
WHEN BLOCKING INTO GATE, SHUTDOWN ENGINE NR 2. COOLING FAN WARNING HORN SOUNDED ALONG WITH LOSS OF RT FMC CDU AND OTHER INSTRUMENTATION. EXTERNAL POWER GROUND POWER AND APU WOULD NOT CONNECT TO AIRPLANE. AFTER WE SHUTDOWN NR 1, WERE ABLE TO CONNECT EXTERNAL POWER AND, OR APU ELECTRICAL POWER. ACFT GROUNDED. COULD NOT DUPLICATE WITH ENGINE RUN AND SHUTDOWN AT GATE. R & R NR 2 BUS TIE BREAKER IAW AMM 24-21-41, C805, TESTS GOOD IAW SAME AND BPCU IAW MM 24-41-21, TESTS GOOD IAW SAME. BOTH PRECAUTIONARY. PERFORMED SYS TEST FOR AC GENERATOR AND CONTROL SYSTEM IAW AMM 24-21-00-700-802 AND OPS TEST FOR THE AC GENERATOR AND CONTROL SYS IAW AMM 24-21-00-700-803. BOTH TESTS GOOD.