Valiant turbomax 824 no hot water CH okay

[Abraham seruwagi]

Hi I have a valiant turbomax 824e that is not producing hot water for the taps.
The central heating works fine, but if I have the CH on or off the hot water doesn't work reliably. It will sometimes fire up and produce some hot water for about 10/20 seconds but very rarely does really hot come out. When I turn the heating on the boiler fires up, Orange light goes on, and starts heating the water. but this does not happen when I just turn the hot water on, no Orange light and no hot water, or orange light comes on for a short period, a bit of warm water and eventually goes cold and light goes out.
I'm guessing it could be the diverter valve and I have changed the Heater exchange in the past 6 years ago.
We haven't changed the scale Inhibitor for a few years until now which will have caused issues.

Any ideas on test I can do to isolate the problem. I possibly could replace the diverter valve but would appreciate any advice before I make any changes.

Thanks Abe

 

[dilalio]

Last service?
Get it diagnosed by a repair tech and have it serviced at the same time. Health check will highlight other issues that may be present/looming.
Would you MOT your own car?

It could be one (or a combination) of several factors and impossible to accurately diagnose without being in front of the appliance.