Morphy richards steam generator iron heating up but steam isnt working as it should?

There is a bad seal on the water reservoir or the steam tank inside the iron.

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https://www.mumsnet.com/Talk/housekeeping/741113-Steam-generator-iron-problems

https://www.morphyrichards.co.uk/Pdf/IB42242.pdf

If tap water is used in a hard water area limescale can soon build up and reduce water flow into the steam generator.
A propriety descaler might help but if the situation is too advanced it is unlikely.

It may be calcified or have lime scale. If the heater is "gummed up", it cannot heat properly. Try using either vinegar (takes longer) or an iron cleaner. You pour it in and it breaks up the scale. CLR works quite well too. Use pipe cleaners to clear out the holes in the sole plate.

do this and use the common sense. God bless you
f the iron heats but steams improperly, inspect the soleplate and clean the vents (see below) and flush sediment out of the steam chamber (see below). If the iron produces too much or too little heat, test the electrical cord . Also test and, if needed, adjust calibration of the thermostat (see the Appliance Controls Fix-It Guide).
If the iron does not spray properly, inspect and clean the nozzle (see below).
If the iron leaks or spits, clean the steam vents, nozzle, and tank.
If the iron sticks to fabric, clean or repair the soleplate. If the iron stains fabric, clean the soleplate, clean the tank with a commercial cleaner, and use distilled or filtered water

My MORPHY RICHARDS 42256 JET STREAM STEAM GENERATOR IRON has stop producing steam. I have changed the filter and although it heats up, it does not produce any steam.

Always switch off the unit and allow to cool before cleaning or storing. .... If your steam generator does not work, check the following points: ... working temperature, the LOW STEAM ICON will flash whilst the heating cycle takes place ... steam. 9 When ironing is complete, press the POWER. STANDBY button.

You can download the manual at
http://www.morphyrichards.co.uk/Downloads/InstructionBooklets/IB42271.PDF