About a indesitwi101

you make no sense. From the picture the water "mixer" is the center lever or is it a diverter valve for the shower and water nozzle below???
The knobs are for hot and cold water??

It is in the mixer system,you may have put in repair kits with new springs,diaphrams,and o-rings or seals(washers).

it could be a water valve fault. try to find out witch one is not letting water in. you can after doing so switch the wiring from the vavles hot to cold. run again. if you were not getting cold water and you switch the wires from cold to hot and now your getting hot when you have the cold on then you know that is a vavle problem. i hope you understand how i put that.

The cold water valve could be faulty. It's quite possible that the valves haven't changed. If you don't need hot water put the HOT hose on the COLD tap and wash on 'hot' or 'warm' you'll need to rinse on hot or warm or the machine wont open the 'hot' valve which is now delivering cold water!!!! Enjoy.........Nomess

I have a triton opal shower.

I turn shower on low pressure and cold water. then no low pressure and piping hot water for a very short time then low pressure and cold water.

I've changed the solenoid and the little black plastic ball.

Help !

there is a little cap on the hot and cold side above the shut off valves, turn the water off at these valve and take the caps off there are filters in there clean them off and reinstall them that should take care of the problem, you might want to flush the tank while your at it hook a hose to the hot side connector and run it out side or to a sump pump then turn on the cold water and flush it out you can also reverse this procedure by doing it on the cold side

most inlet water hoses have screens in them.  You could remove the hose from the back of the washer and see if there is water flow.   If there isn't, the hot water valve assembly is defective.  These are solenoid operated valves that admit water into the tub.  They can be accessed behind the washer after you remove the back.   

what u need to do is let the flow and return pipes for the heating go cold they are normally the 22mm ones and if 1 gets warm when u run your hot tap then u need a new diverter valve. if they stay cold then u need to see if the boiler is igniting in hot water so turn off the heating and just run the hot tap to see if it ignites get back to me

probably just coincidence.
you will have to check cold valve is ok with a multimeter

can you check some other source of hot water? if the pressure there is ok?..if it is, then the problem is on the new tap that you fitted.