no steam only air bubbles sometimes only the odd squirt of water polti 2000?

I would guess that the solenoid valve is blocked with limescale. This can be a gradual build up especially with hard water or can be a piece trapped inside, normally after it has been tipped upside down to empty out the gunge....You will still get water coming through as the valve aperture is reduced and may be condensing the steam into water droplets. It can be cleaned out if you can get access.

Malcolm X
September 2007