Triton Power Shower Thermostatic hot water problem

[Falklander]

A couple of nights ago my Triton Power Shower Thermostatic developed a problem. It has been installed for over 4 years and we have not had problems with it before. There is a loss of hot water pressure coming out of the shower head. I have checked and cleaned the filters, and whilst they were out turned the hot water slightly on to see if the flow was restricted but it seemed fine. Don't think the pump can be the problem as there is still plenty of force with the cold, but when you turn the control towards the hot then the flow goes down to about a third or less of what it should be. The pressure to all the hot taps in the house is fine so don't believe there is air in the system. Any ideas please.

 

[seco services]

I have checked and cleaned the filters, and whilst they were out turned the hot water slightly on to see if the flow was restricted but it seemed fine.

You need to turn it fully on to clear any air if any.
Compare it to the cold flow.

Also poss a stuck non return valve, Which are located just after the filters.
What type of isolate valves have you on the pipework ? ballofix, gate valves etc.

 

[Falklander]

Tried turning supply full on, both hot and cold flow fine although we have more pressure on the cold than the hot but it has always been like that. Took out the temperature control valve and cleaned it, slight bit of detritus on filters on this but not much. Put back together an it seemed worse with the cold flow reduced too. Took to pieces again, and removed motor and pump. Opened pump and checked but nothing jammed in it and looked clean. Put everything back together, switched on and cold is fine again but still same problem with the hot.

To isolate the water from the shower we have half inch fittings in the pipes that you turn with a screw driver to open or close them. The flow to the shower is fine through both of these when they are turned on as we checked it when the filters were out.

Thank you for you previous help, any other suggestions?