Undo the 4 screws on the front and carefully pull the front cover off. It has a rubber gasket which can tear.
There is a blue dash pot on the circuit board which is the adjuster. You need a very small screwdriver to turn it. If you look very carefully there is an arrow and either numbers or letters on the outside of the dial - I can't remember which. The higher the letters/figures the higher the pressure, so just turn it down a couple of letters/figures and try it.