Air Assisted Suspension Query

I have a 2000 Niesmann+Bischoff Arto 69 with an Airide system fitted. The vehicle has a slight lean to the right so I suspect that side needs more air: however I have no information on what needs to be done. There is a pressure gauge, valve and separate red and blue lines with 'taps' fitted just inside the doorway. Hopefully a picture is attached.

Is anyone familiar with this type of installation and what needs to be done. The gauge currently indicates about 45psi/3.2bar - there is only one needle.

Many thanks for any assistance.

 

Move the red valve into the down position and note the reading then shut the valve off again, do the same with the blue valve and compare the readings. Whichever is the lessor, open that valve and fit a pump or a compressor to the valve inlet after removing the metal valve cap and fill to equal pressure as the other side.

 

hopefully its just uneven on the airbags but a pronounced list also indicates a torsion bar suspension spring may have failed on an alko chassis