Fix Fault Vauxhall

i have replaced three new cooling switches in 7 months is this a problem with the units or what also my temprature gauge get to the red section before the fan cuts in can you give me any help wi ... more

why i have a big presure o the cooling pipe,is normal ,the car is a vauxhall vectra tdi 2l 2001

my cooling fan comes on and stays on when i switch the ignition on how do i fix it ?