faulty shower or faulty boiler ??

[Illy]

Heating engineer came to fix an issue with our combi-boiler....and now the mixer shower isn't working properly. Basically the shower only gets hot either when we put a hot tap on at the same time as the shower, or the boiler is in heating/hot water mode. It will not work when the boiler is just in hot water mode. Strange thing is the hot taps in the kitchen and bathroom do work when the boiler is in hot water mode....just no the shower!

The shower is a few years old and the heating engineer says it's the thermostat in the shower that's faulty, but I'm not buying this as it has only occurred since there was an issue with the boiler (which has now been fixed)

I think it's that the boiler isn't 'speaking' / connecting with the shower properly when it demands hot water. Surely if the thermostat wasn't working the shower wouldn't get hot at all

If I get a new shower and then the problem still exists then it proves that the issue is with the boiler, and I have just bought a new shower for no reason. This is my fear.

any advice welcome thanks

 

[Tonycane]

What was the issue with the boiler? If the other hot outlets are fine the boiler is doing its job and points to the shower. Might just need the filters cleaning out or a new cartridge depending on its age?
does the boiler fire up when the showers running?