What was found
WITH BOTH ENGINES RUNNING, BOTH PACKS AUTO ISOLATION VALVE AUTO, BOTH ENGINE BLEED VALVES ON, LEFT DUCT PRESSURE 0 PSI, RIGHT 20 PSI. GROUNDED - YES. PERFORMED B737-800 FIM 36-10 TASK 805 FOUND CONNECTOR ON BLEED AIR REGULATOR DISCONNECTED, RECONNECTED CONNECTOR. PERFORMED ENGINE RUN ALL INDICATIONS NORMAL.