What was found
AIR TURNBACK AFTER LIFTOFF, SHORTLY AFTER LANDING GEAR UP, BOTH "A" ELECTRIC & ENGINE DRIVEN HYDRAULIC LOW PRESSURE LIGHTS CAME ON. HYDRAULIC PRESSURE & QUANTITY ON GAUGES NORMAL. ELECTRIC DRIVEN LIGHT WENT OUT IN ABOUT 5 SECONDS, THEN ENGINE DRIVEN LIGHT WENT OUT 5 SECONDS LATER. WHEN LANDING GEAR DOWN GOT ENGINE DRIVEN LOW PRESSURE LIGHT ON FOR ABOUT 3 SECONDS, THEN OUT. R&R HYDRAULIC RESERVOIR VENT VALVE & ADAPTER CAP FOR "A" SYSTEM IAW AMM.