Hydraulic systems issue

In my case all of the hydraulic pumps switches seem to be ineffective, or I'm doing something wrong.Situation 1 : initial state of the ngx (engine runing)If i switch off system A and B hydraulic pumps, none of the low pressure indicators for hydraulic systems will illuminate, and flight controls low pressure indicators neither.The systems page on the lower DU shows a pressure of 2900 psi that never decreases by the time : all flight controls remain fully operational even after a long time (10 minutes). Howerver the elictrical motor driven hydraulic pumps consume power: the amperage decreases if i switch them off (metered on the electrical metering panel). Situation 2 : ngx set to cold and dark (via the cdu panel state load)I close the opened guarded switches, i start the apu, then let it provide electricity and bleed air (both apu gen switches on - apu bleed air valve open - pneumatic isolation valve open).Flight controls low pressure indicators are illuminated, none of the low pressure indicators for hydraulic systems are illuminated. The systems page on the lower DU shows a hydraulic pressure of 50 psi. The flight controls are not fully operational.If i switch the elictrical motor driven hydraulic pumps to on, nothing changes exept the power consumption.After engine start nothing changes.I also thaught the normal hydraulic pressure was 3000 psi not 2900 psi.